118-467: Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including cats (large and small), hyenas , mongooses , viverrids , and related taxa . Feliformia stands in contrast to the other suborder of Carnivora, Caniformia (also Canoidea, "dog-like" carnivorans). The separation of the Carnivora into the broad groups of feliforms and caniforms is widely accepted, as
236-581: A septum . Caniforms have single-chambered or partially divided auditory bullae, composed of a single bone. Initially, the early representatives of carnivorans were small as the creodonts (specifically, the oxyaenids) and mesonychians dominated the apex predator niches during the Eocene, but in the Oligocene, carnivorans became a dominant group of apex predators with the nimravids , and by the Miocene most of
354-445: A buffer to recruit or titrate ions or antibiotics. Extracellular DNA acts as a functional extracellular matrix component in the biofilms of several bacterial species. It may act as a recognition factor to regulate the attachment and dispersal of specific cell types in the biofilm; it may contribute to biofilm formation; and it may contribute to the biofilm's physical strength and resistance to biological stress. Cell-free fetal DNA
472-462: A cell makes up its genome ; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. The information carried by DNA is held in the sequence of pieces of DNA called genes . Transmission of genetic information in genes is achieved via complementary base pairing. For example, in transcription, when a cell uses the information in a gene, the DNA sequence is copied into
590-450: A chain by covalent bonds (known as the phosphodiester linkage ) between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone . The nitrogenous bases of the two separate polynucleotide strands are bound together, according to base pairing rules (A with T and C with G), with hydrogen bonds to make double-stranded DNA. The complementary nitrogenous bases are divided into two groups,
708-445: A complementary RNA sequence through the attraction between the DNA and the correct RNA nucleotides. Usually, this RNA copy is then used to make a matching protein sequence in a process called translation , which depends on the same interaction between RNA nucleotides. In an alternative fashion, a cell may copy its genetic information in a process called DNA replication . The details of these functions are covered in other articles; here
826-440: A correlation between habitat and color pattern; for example spotted or banded species tend to be found in heavily forested environments. Some species like the grey wolf are polymorphic with different individual having different coat colors. The arctic fox ( Vulpes lagopus ) and the stoat ( Mustela erminea ) have fur that changes from white and dense in the winter to brown and sparse in the summer. In pinnipeds and polar bears ,
944-492: A double helix can thus be pulled apart like a zipper, either by a mechanical force or high temperature . As a result of this base pair complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. This reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in organisms. Most DNA molecules are actually two polymer strands, bound together in
1062-428: A full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules. Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500. However, the amount of mitochondria per cell also varies by cell type, and an egg cell can contain 100,000 mitochondria, corresponding to up to 1,500,000 copies of
1180-439: A helical fashion by noncovalent bonds; this double-stranded (dsDNA) structure is maintained largely by the intrastrand base stacking interactions, which are strongest for G,C stacks. The two strands can come apart—a process known as melting—to form two single-stranded DNA (ssDNA) molecules. Melting occurs at high temperatures, low salt and high pH (low pH also melts DNA, but since DNA is unstable due to acid depurination, low pH
1298-571: A higher number is also possible but this would be against the natural principle of least effort . The phosphate groups of DNA give it similar acidic properties to phosphoric acid and it can be considered as a strong acid . It will be fully ionized at a normal cellular pH, releasing protons which leave behind negative charges on the phosphate groups. These negative charges protect DNA from breakdown by hydrolysis by repelling nucleophiles which could hydrolyze it. Pure DNA extracted from cells forms white, stringy clumps. The expression of genes
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#17327869154311416-667: A long-standing puzzle known as the " C-value enigma ". However, some DNA sequences that do not code protein may still encode functional non-coding RNA molecules, which are involved in the regulation of gene expression . Some noncoding DNA sequences play structural roles in chromosomes. Telomeres and centromeres typically contain few genes but are important for the function and stability of chromosomes. An abundant form of noncoding DNA in humans are pseudogenes , which are copies of genes that have been disabled by mutation. These sequences are usually just molecular fossils , although they can occasionally serve as raw genetic material for
1534-409: A narrower, deeper major groove. The A form occurs under non-physiological conditions in partly dehydrated samples of DNA, while in the cell it may be produced in hybrid pairings of DNA and RNA strands, and in enzyme-DNA complexes. Segments of DNA where the bases have been chemically modified by methylation may undergo a larger change in conformation and adopt the Z form . Here, the strands turn about
1652-442: A radius of 10 Å (1.0 nm). According to another study, when measured in a different solution, the DNA chain measured 22–26 Å (2.2–2.6 nm) wide, and one nucleotide unit measured 3.3 Å (0.33 nm) long. The buoyant density of most DNA is 1.7g/cm . DNA does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. These two long strands coil around each other, in
1770-416: A second protein when read in the opposite direction along the other strand. In bacteria , this overlap may be involved in the regulation of gene transcription, while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome. DNA can be twisted like a rope in a process called DNA supercoiling . With DNA in its "relaxed" state, a strand usually circles
1888-445: A simple TTAGGG sequence. These guanine-rich sequences may stabilize chromosome ends by forming structures of stacked sets of four-base units, rather than the usual base pairs found in other DNA molecules. Here, four guanine bases, known as a guanine tetrad , form a flat plate. These flat four-base units then stack on top of each other to form a stable G-quadruplex structure. These structures are stabilized by hydrogen bonding between
2006-411: A single bone. This feature, however, is problematic for the classification of the extinct Nimravidae as feliforms. Nimravid fossils show ossified bullae with no septum, or no trace at all of the entire bulla. It is assumed that they had a cartilaginous housing of the ear mechanism. The specific characteristics of extant feliform bullae suggest a common ancestor, though one has not been identified in
2124-552: A single common ancestor that was a herpestid (Yoder et al. 2003). Phylogenetic analysis supports this view and places all of the Malagasy carnivorans in the family Eupleridae. The differences in form make it difficult to concisely summarise the species in this family. The range in size is as diverse as the range in form, with smaller species at less than 500 g (1 lb) and the largest species at up to 12 kg (26 lb). Some have retractile or semi-retractile claws (the fossa and
2242-473: A supporting amount of evidence that Miacoidea is an evolutionary grade of carnivoramorphs that, while viverravids are monophyletic basal group, the miacids are paraphyletic in respect to Carnivora (as shown in the phylogeny below). Carnivoramorpha as a whole first appeared in the Paleocene of North America about 60 million years ago. Crown carnivorans first appeared around 42 million years ago in
2360-442: A thick insulating layer of blubber helps maintain their body temperature. Carnivorans are arguably the group of mammals of most interest to humans. The dog is noteworthy for not only being the first species of carnivoran to be domesticated , but also the first species of any taxon. In the last 10,000 to 12,000 years, humans have selectively bred dogs for a variety of different tasks and today there are well over 400 breeds. The cat
2478-646: A wide array of body plans, varying greatly in size and shape. Carnivora are divided into two suborders , the Feliformia , containing the true felids and several " cat -like" animals; and the Caniformia , containing the true canids and many " dog -like" animals. The feliforms include the Felidae , Viverridae , hyena , and mongoose families, the majority of which live only in the Old World; cats are
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#17327869154312596-413: Is a polymer composed of two polynucleotide chains that coil around each other to form a double helix . The polymer carries genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses . DNA and ribonucleic acid (RNA) are nucleic acids . Alongside proteins , lipids and complex carbohydrates ( polysaccharides ), nucleic acids are one of
2714-762: Is a polyphyletic family of extinct viverrid -like feliforms. The phylogenetic relationships of feliforms are shown in the following cladogram † Nimravidae (false saber-toothed cats) [REDACTED] Nandiniidae (African palm civet) [REDACTED] Viverridae (viverrids) [REDACTED] Herpestidae (mongooses) [REDACTED] Eupleridae (Malagasy mongooses) [REDACTED] † Lophocyonidae † Percrocutidae [REDACTED] Hyaenidae (hyenas) [REDACTED] † Haplogale Prionodontidae (Asiatic linsangs) [REDACTED] † Barbourofelidae † Stenogale Felidae (cats) [REDACTED] Carnivora Carnivora ( / k ɑːr ˈ n ɪ v ər ə / kar- NIH -vər-ə )
2832-682: Is a table chart of the extant carnivoran families and number of extant species recognized by various authors of the first (2009 ) and fourth (2014 ) volumes of the Handbook of the Mammals of the World : The canine teeth are usually large, conical, thick and stress resistant. All of the terrestrial species of carnivorans have three incisors on each side of each jaw (the exception is the sea otter ( Enhydra lutris ) which only has two lower incisor teeth). The third molar has been lost. The carnassial pair
2950-486: Is an order of placental mammals that have specialized in primarily eating flesh, whose members are formally referred to as carnivorans . The order Carnivora is the sixth largest order of mammals, comprising at least 279 species on every major landmass and in a variety of habitats, ranging from the cold polar regions of Earth to the hyper-arid region of the Sahara Desert and the open seas. Carnivorans exhibit
3068-475: Is another domesticated carnivoran and it is today considered one of the most successful species on the planet, due to their close proximity to humans and the popularity of cats as pets. Many other species are popular, and they are often charismatic megafauna . Many civilizations have incorporated a species of carnivoran into their culture: a prominent example is the lion , viewed as a symbol of power and royalty in many societies. Yet many species such as wolves and
3186-447: Is called intercalation . Most intercalators are aromatic and planar molecules; examples include ethidium bromide , acridines , daunomycin , and doxorubicin . For an intercalator to fit between base pairs, the bases must separate, distorting the DNA strands by unwinding of the double helix. This inhibits both transcription and DNA replication, causing toxicity and mutations. As a result, DNA intercalators may be carcinogens , and in
3304-435: Is called a polynucleotide . The backbone of the DNA strand is made from alternating phosphate and sugar groups. The sugar in DNA is 2-deoxyribose , which is a pentose (five- carbon ) sugar. The sugars are joined by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These are known as the 3′-end (three prime end), and 5′-end (five prime end) carbons,
3422-434: Is dependent on ionic strength and the concentration of DNA. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determines the strength of the association between the two strands of DNA. Long DNA helices with a high GC -content have more strongly interacting strands, while short helices with high AT content have more weakly interacting strands. In biology, parts of
3540-411: Is influenced by how the DNA is packaged in chromosomes, in a structure called chromatin . Base modifications can be involved in packaging, with regions that have low or no gene expression usually containing high levels of methylation of cytosine bases. DNA packaging and its influence on gene expression can also occur by covalent modifications of the histone protein core around which DNA is wrapped in
3658-432: Is introduced by enzymes called topoisomerases . These enzymes are also needed to relieve the twisting stresses introduced into DNA strands during processes such as transcription and DNA replication . DNA exists in many possible conformations that include A-DNA , B-DNA , and Z-DNA forms, although only B-DNA and Z-DNA have been directly observed in functional organisms. The conformation that DNA adopts depends on
Feliformia - Misplaced Pages Continue
3776-428: Is made up of the fourth upper premolar and the first lower molar teeth. Like most mammals, the dentition is heterodont , though in some species, such as the aardwolf ( Proteles cristata ), the teeth have been greatly reduced and the cheek teeth are specialised for eating insects. In pinnipeds, the teeth are homodont as they have evolved to grasp or catch fish, and the cheek teeth are often lost. In bears and raccoons,
3894-540: Is no clear common ancestor of the Feliform families in the fossil records. As forest dwellers, the early Feliforms were subject to more rapid decomposition in the absence of sedimentary materials, resulting in large gaps in the fossil records. For more discussion on feliform evolution and the divergence from the caniforms, together with additional external references on this subject, see the articles on Carnivora , Miacoidea and Carnivoramorpha . Family Stenoplesictidae
4012-422: Is nothing special about the four natural nucleobases that evolved on Earth. On the other hand, DNA is tightly related to RNA which does not only act as a transcript of DNA but also performs as molecular machines many tasks in cells. For this purpose it has to fold into a structure. It has been shown that to allow to create all possible structures at least four bases are required for the corresponding RNA , while
4130-432: Is one of four types of nucleobases (or bases ). It is the sequence of these four nucleobases along the backbone that encodes genetic information. RNA strands are created using DNA strands as a template in a process called transcription , where DNA bases are exchanged for their corresponding bases except in the case of thymine (T), for which RNA substitutes uracil (U). Under the genetic code , these RNA strands specify
4248-517: Is rarely used). The stability of the dsDNA form depends not only on the GC -content (% G,C basepairs) but also on sequence (since stacking is sequence specific) and also length (longer molecules are more stable). The stability can be measured in various ways; a common way is the melting temperature (also called T m value), which is the temperature at which 50% of the double-strand molecules are converted to single-strand molecules; melting temperature
4366-428: Is recreated by an enzyme called DNA polymerase . This enzyme makes the complementary strand by finding the correct base through complementary base pairing and bonding it onto the original strand. As DNA polymerases can only extend a DNA strand in a 5′ to 3′ direction, different mechanisms are used to copy the antiparallel strands of the double helix. In this way, the base on the old strand dictates which base appears on
4484-641: Is the definition of Feliformia and Caniformia as suborders (sometimes superfamilies). The classification of feliforms as part of the Feliformia suborder or under separate groupings continues to evolve. Systematic classifications dealing with only extant taxa include all feliforms into the Feliformia suborder, though variations exist in the definition and grouping of families and genera. Indeed, molecular phylogenies suggest that all extant Feliformia are monophyletic . Systematic classifications dealing with both extant and extinct taxa vary more widely. Some separate
4602-516: Is the largest human chromosome with approximately 220 million base pairs , and would be 85 mm long if straightened. In eukaryotes , in addition to nuclear DNA , there is also mitochondrial DNA (mtDNA) which encodes certain proteins used by the mitochondria. The mtDNA is usually relatively small in comparison to the nuclear DNA. For example, the human mitochondrial DNA forms closed circular molecules, each of which contains 16,569 DNA base pairs, with each such molecule normally containing
4720-489: Is to allow the cell to replicate chromosome ends using the enzyme telomerase , as the enzymes that normally replicate DNA cannot copy the extreme 3′ ends of chromosomes. These specialized chromosome caps also help protect the DNA ends, and stop the DNA repair systems in the cell from treating them as damage to be corrected. In human cells , telomeres are usually lengths of single-stranded DNA containing several thousand repeats of
4838-474: The Caribbean monk seal ( Neomonachus tropicalis ) in 1952. Some species such as the red fox ( Vulpes vulpes ) and stoat ( Mustela erminea ) have been introduced to Australasia and have caused many native species to become endangered or even extinct. DNA Deoxyribonucleic acid ( / d iː ˈ ɒ k s ɪ ˌ r aɪ b oʊ nj uː ˌ k l iː ɪ k , - ˌ k l eɪ -/ ; DNA )
Feliformia - Misplaced Pages Continue
4956-477: The Cretaceous–Paleogene extinction event . These early ancestors of carnivorans would have resembled small weasel or genet -like mammals, occupying a nocturnal shift on the forest floor or in the trees, as other groups of mammals like the mesonychians and later the creodonts were occupying the megafaunal faunivorous niche. However, following the extinction of mesonychians and the oxyaenid creodonts at
5074-657: The DNA sequence . Mutagens include oxidizing agents , alkylating agents and also high-energy electromagnetic radiation such as ultraviolet light and X-rays . The type of DNA damage produced depends on the type of mutagen. For example, UV light can damage DNA by producing thymine dimers , which are cross-links between pyrimidine bases. On the other hand, oxidants such as free radicals or hydrogen peroxide produce multiple forms of damage, including base modifications, particularly of guanosine, and double-strand breaks. A typical human cell contains about 150,000 bases that have suffered oxidative damage. Of these oxidative lesions,
5192-520: The Middle East , India and Africa . Hyenas are large, powerful animals, up to 80 kg (176 lb) and represent one of the most prolific large carnivorans on the planet. The aardwolf is much smaller and is a specialised feeder, eating mainly harvester termites. Family Herpestidae ( mongooses , kusimanses , and the meerkat ) has 32 species. Previously, these were placed in the family Viverridae. However, Wilson and Reeder (1993) established
5310-558: The Middle Eocene . Their molecular phylogeny shows the extant Carnivora are a monophyletic group, the crown group of the Carnivoramorpha . From there carnivorans have split into two clades based on the composition of the bony structures that surround the middle ear of the skull, the cat-like feliforms and the dog-like caniforms . In feliforms, the auditory bullae are double-chambered, composed of two bones joined by
5428-406: The amino-acid sequences of proteins is determined by the rules of translation , known collectively as the genetic code . The genetic code consists of three-letter 'words' called codons formed from a sequence of three nucleotides (e.g. ACT, CAG, TTT). In transcription, the codons of a gene are copied into messenger RNA by RNA polymerase . This RNA copy is then decoded by a ribosome that reads
5546-487: The big cats have been broadly hunted, resulting in extirpation in some areas. Habitat loss and human encroachment as well as climate change have been the primary cause of many species going into decline. Four species of carnivorans have gone extinct since the 1600s: Falkland Island wolf ( Dusicyon australis ) in 1876; the sea mink ( Neogale macrodon ) in 1894; the Japanese sea lion ( Zalophus japonicus ) in 1951 and
5664-469: The cell nucleus as nuclear DNA , and some in the mitochondria as mitochondrial DNA or in chloroplasts as chloroplast DNA . In contrast, prokaryotes ( bacteria and archaea ) store their DNA only in the cytoplasm , in circular chromosomes . Within eukaryotic chromosomes, chromatin proteins, such as histones , compact and organize DNA. These compacting structures guide the interactions between DNA and other proteins, helping control which parts of
5782-535: The fossil records. There are other characteristics that differentiate feliforms from caniforms and probably existed in their stem taxa. But, due to speciation, these do not apply unambiguously to all extant species. Feliforms tend to have shorter rostrums (snouts) than caniforms, fewer teeth, and more specialized carnassials . Feliforms tend to be more carnivorous and are generally ambush hunters. Caniforms tend more toward omnivorous and opportunity-based feeding. However, omnivorous feliforms also exist, particularly in
5900-752: The "cat-like" carnivorans. There are 41 extant species, and all but a few have retractile claws. This family is represented on all continents except for Australia (where domestic cats have been introduced ) and Antarctica. The species vary in size from the tiny black-footed cat ( Felis nigripes ) at only 2 kg (4.5 lb) to the tiger ( Panthera tigris ) at 300 kg (660 lb). Diet ranges from large to small mammals, birds and insects (depending on species size). Family Hyaenidae ( hyenas and aardwolf ) has four extant species and two subspecies. All show features of convergent evolution with canids , including non-retractile claws, long muzzles, and adaptations to running for long distances. They are extant in
6018-419: The 3′ and 5′ carbons along the sugar-phosphate backbone confers directionality (sometimes called polarity) to each DNA strand. In a nucleic acid double helix , the direction of the nucleotides in one strand is opposite to their direction in the other strand: the strands are antiparallel . The asymmetric ends of DNA strands are said to have a directionality of five prime end (5′ ), and three prime end (3′), with
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#17327869154316136-591: The 5′ end having a terminal phosphate group and the 3′ end a terminal hydroxyl group. One major difference between DNA and RNA is the sugar, with the 2-deoxyribose in DNA being replaced by the related pentose sugar ribose in RNA. The DNA double helix is stabilized primarily by two forces: hydrogen bonds between nucleotides and base-stacking interactions among aromatic nucleobases. The four bases found in DNA are adenine ( A ), cytosine ( C ), guanine ( G ) and thymine ( T ). These four bases are attached to
6254-435: The DNA are transcribed. DNA is a long polymer made from repeating units called nucleotides . The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. In all species it is composed of two helical chains, bound to each other by hydrogen bonds . Both chains are coiled around the same axis, and have the same pitch of 34 ångströms (3.4 nm ). The pair of chains have
6372-460: The DNA double helix that need to separate easily, such as the TATAAT Pribnow box in some promoters , tend to have a high AT content, making the strands easier to pull apart. In the laboratory, the strength of this interaction can be measured by finding the melting temperature T m necessary to break half of the hydrogen bonds. When all the base pairs in a DNA double helix melt,
6490-405: The Malagasy civet) and others do not (the falanouc and Malagasy mongooses). They all tend to have slender bodies and pointed rostra (except the fossa, which has a blunt snout). Diet varies with size and form of the species and, like their mainland counterparts, ranges from small mammals, insects and invertebrates through to crustaceans and molluscs. Family Felidae (cats) are the most widespread of
6608-401: The RNA sequence by base-pairing the messenger RNA to transfer RNA , which carries amino acids. Since there are 4 bases in 3-letter combinations, there are 64 possible codons (4 combinations). These encode the twenty standard amino acids , giving most amino acids more than one possible codon. There are also three 'stop' or 'nonsense' codons signifying the end of the coding region; these are
6726-491: The TAG, TAA, and TGA codons, (UAG, UAA, and UGA on the mRNA). Cell division is essential for an organism to grow, but, when a cell divides, it must replicate the DNA in its genome so that the two daughter cells have the same genetic information as their parent. The double-stranded structure of DNA provides a simple mechanism for DNA replication . Here, the two strands are separated and then each strand's complementary DNA sequence
6844-442: The axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound. If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together. If they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily. In nature, most DNA has slight negative supercoiling that
6962-407: The canonical bases plus uracil. Twin helical strands form the DNA backbone. Another double helix may be found tracing the spaces, or grooves, between the strands. These voids are adjacent to the base pairs and may provide a binding site . As the strands are not symmetrically located with respect to each other, the grooves are unequally sized. The major groove is 22 ångströms (2.2 nm) wide, while
7080-406: The carnassial pair is secondarily reduced. The skulls are heavily built with a strong zygomatic arch . Often a sagittal crest is present, sometimes more evident in sexually dimorphic species such as sea lions and fur seals , though it has also been greatly reduced in some small carnivorans. The braincase is enlarged with the frontoparietal bone at the front. In most species, the eyes are at
7198-467: The case of thalidomide, a teratogen . Others such as benzo[ a ]pyrene diol epoxide and aflatoxin form DNA adducts that induce errors in replication. Nevertheless, due to their ability to inhibit DNA transcription and replication, other similar toxins are also used in chemotherapy to inhibit rapidly growing cancer cells. DNA usually occurs as linear chromosomes in eukaryotes , and circular chromosomes in prokaryotes . The set of chromosomes in
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#17327869154317316-591: The case. In the Middle Eocene (about 42 mya), the miacids started to branch into two distinct groups of the order Carnivora: the Feliforms and Caniforms. The miacid precursors to the extant Feliforms remained forest-dwelling, arboreal or semi-arboreal ambush hunters, while the Caniform precursors were more mobile, opportunistic hunters. While it is clear that the first Feliforms appeared at this time, there
7434-581: The cell (see below) , but the major and minor grooves are always named to reflect the differences in width that would be seen if the DNA was twisted back into the ordinary B form . In a DNA double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand. This is called complementary base pairing . Purines form hydrogen bonds to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds. This arrangement of two nucleotides binding together across
7552-619: The chromatin structure or else by remodeling carried out by chromatin remodeling complexes (see Chromatin remodeling ). There is, further, crosstalk between DNA methylation and histone modification, so they can coordinately affect chromatin and gene expression. For one example, cytosine methylation produces 5-methylcytosine , which is important for X-inactivation of chromosomes. The average level of methylation varies between organisms—the worm Caenorhabditis elegans lacks cytosine methylation, while vertebrates have higher levels, with up to 1% of their DNA containing 5-methylcytosine. Despite
7670-403: The clade Ferae . Ferae includes the closest extant relative of carnivorans, the pangolins , as well as several extinct groups of mostly Paleogene carnivorous placentals such as the creodonts , the arctocyonians , and mesonychians . The creodonts were originally thought of as the sister taxon to the carnivorans, perhaps even ancestral to, based on the presence of the carnassial teeth , but
7788-480: The conditions found in cells, it is not a well-defined conformation but a family of related DNA conformations that occur at the high hydration levels present in cells. Their corresponding X-ray diffraction and scattering patterns are characteristic of molecular paracrystals with a significant degree of disorder. Compared to B-DNA, the A-DNA form is a wider right-handed spiral, with a shallow, wide minor groove and
7906-405: The creation of new genes through the process of gene duplication and divergence . A gene is a sequence of DNA that contains genetic information and can influence the phenotype of an organism. Within a gene, the sequence of bases along a DNA strand defines a messenger RNA sequence, which then defines one or more protein sequences. The relationship between the nucleotide sequences of genes and
8024-449: The cytoplasm called the nucleoid . The genetic information in a genome is held within genes, and the complete set of this information in an organism is called its genotype . A gene is a unit of heredity and is a region of DNA that influences a particular characteristic in an organism. Genes contain an open reading frame that can be transcribed, and regulatory sequences such as promoters and enhancers , which control transcription of
8142-443: The dental and cranial features, not much of their overall anatomy unites carnivorans as a group. All species of carnivorans are quadrupedal and most have five digits on the front feet and four digits on the back feet. In terrestrial carnivorans, the feet have soft pads. The feet can either be digitigrade as seen in cats, hyenas and dogs or plantigrade as seen in bears, skunks, raccoons, weasels, civets and mongooses. In pinnipeds,
8260-405: The double helix (from six-carbon ring to six-carbon ring) is called a Watson-Crick base pair. DNA with high GC-content is more stable than DNA with low GC -content. A Hoogsteen base pair (hydrogen bonding the 6-carbon ring to the 5-carbon ring) is a rare variation of base-pairing. As hydrogen bonds are not covalent , they can be broken and rejoined relatively easily. The two strands of DNA in
8378-442: The edges of the bases and chelation of a metal ion in the centre of each four-base unit. Other structures can also be formed, with the central set of four bases coming from either a single strand folded around the bases, or several different parallel strands, each contributing one base to the central structure. In addition to these stacked structures, telomeres also form large loop structures called telomere loops, or T-loops. Here,
8496-481: The end of an otherwise complementary double-strand of DNA. However, branched DNA can occur if a third strand of DNA is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre-existing double-strand. Although the simplest example of branched DNA involves only three strands of DNA, complexes involving additional strands and multiple branches are also possible. Branched DNA can be used in nanotechnology to construct geometric shapes, see
8614-482: The end of the Eocene, carnivorans quickly moved into this niche, with forms like the nimravids being the dominant large-bodied ambush predators during the Oligocene alongside the hyaenodont creodonts (which similarly produced larger, more open-country forms at the start of the Oligocene). By the time Miocene epoch appeared, most if not all of the major lineages and families of carnivorans had diversified and become
8732-759: The extant carnivoran families have diversified and become the primary terrestrial predators in the Northern Hemisphere. In 1758, the Swedish botanist Carl Linnaeus placed all carnivorans known at the time into the group Ferae (not to be confused with the modern concept of Ferae which also includes pangolins) in the tenth edition of his book Systema Naturae . He recognized six genera: Canis (canids and hyaenids), Phoca (pinnipeds), Felis (felids), Viverra (viverrids, herpestids, and mephitids), Mustela (non-badger mustelids), Ursus (ursids, large species of mustelids, and procyonids). It
8850-518: The family Viverridae . Many feliforms have retractile or semi-retractile claws and many are arboreal or semi-arboreal. Feliforms also tend to be more digitigrade (walking on toes). Most caniforms are terrestrial and have non-retractile claws. Seven families are extant, with 12 subfamilies, 56 genera, and 114 species in the Feliformia suborder. They range natively across all continents except Australia and Antarctica . Most species are arboreal or semiarboreal ambush hunters. Target prey vary based on
8968-445: The feliforms (extant and extinct) as Aeluroidea (superfamily) and Feliformia (suborder). Others include all feliforms (extant, extinct and "possible ancestors") into the Feliformia suborder. Some studies suggest this inclusion of "possible ancestors" into Feliformia (or even Carnivora) may be spurious. The extinct (†) families as reflected in the taxa chart are the least problematic in terms of their relationship with extant feliforms (with
9086-418: The focus is on the interactions between DNA and other molecules that mediate the function of the genome. Genomic DNA is tightly and orderly packed in the process called DNA condensation , to fit the small available volumes of the cell. In eukaryotes, DNA is located in the cell nucleus , with small amounts in mitochondria and chloroplasts . In prokaryotes, the DNA is held within an irregularly shaped body in
9204-461: The four major types of macromolecules that are essential for all known forms of life . The two DNA strands are known as polynucleotides as they are composed of simpler monomeric units called nucleotides . Each nucleotide is composed of one of four nitrogen-containing nucleobases ( cytosine [C], guanine [G], adenine [A] or thymine [T]), a sugar called deoxyribose , and a phosphate group . The nucleotides are joined to one another in
9322-407: The front of the face. In caniforms, the rostrum is usually long with many teeth, while in feliforms it is shorter with fewer teeth. The carnassial teeth of feliforms are generally more sectional than those of caniforms. The turbinates are large and complex in comparison to other mammals, providing a large surface area for olfactory receptors . Aside from an accumulation of characteristics in
9440-448: The functions of these RNAs are not entirely clear. One proposal is that antisense RNAs are involved in regulating gene expression through RNA-RNA base pairing. A few DNA sequences in prokaryotes and eukaryotes, and more in plasmids and viruses , blur the distinction between sense and antisense strands by having overlapping genes . In these cases, some DNA sequences do double duty, encoding one protein when read along one strand, and
9558-448: The helical axis in a left-handed spiral, the opposite of the more common B form. These unusual structures can be recognized by specific Z-DNA binding proteins and may be involved in the regulation of transcription. For many years, exobiologists have proposed the existence of a shadow biosphere , a postulated microbial biosphere of Earth that uses radically different biochemical and molecular processes than currently known life. One of
9676-897: The herpestids as morphologically and genetically distinct from viverrids. They are extant in Africa, Middle East and Asia . All have non-retractile claws. They are smaller as a family, ranging from 1 kg (2.2 lb) to 5 kg (11 lb), and typically have long, slender bodies and short legs. Diet varies based on species size and available food sources, ranging from small mammals, birds to reptiles , insects and crabs . Some species are omnivorous , including fruits and tubers in their diet. Family Nandiniidae (the African palm civet ) has only one species ( Nandinia binotata ), extant across sub-Saharan Africa . They have retractile claws and are slender-bodied, arboreal omnivores (with fruit making up much of their diet). They are relatively small with
9794-448: The hydration level, DNA sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and concentration of metal ions , and the presence of polyamines in solution. The first published reports of A-DNA X-ray diffraction patterns —and also B-DNA—used analyses based on Patterson functions that provided only a limited amount of structural information for oriented fibers of DNA. An alternative analysis
9912-427: The hydrolytic activities of cellular water, etc., also occur frequently. Although most of these damages are repaired, in any cell some DNA damage may remain despite the action of repair processes. These remaining DNA damages accumulate with age in mammalian postmitotic tissues. This accumulation appears to be an important underlying cause of aging. Many mutagens fit into the space between two adjacent base pairs, this
10030-412: The importance of 5-methylcytosine, it can deaminate to leave a thymine base, so methylated cytosines are particularly prone to mutations . Other base modifications include adenine methylation in bacteria, the presence of 5-hydroxymethylcytosine in the brain , and the glycosylation of uracil to produce the "J-base" in kinetoplastids . DNA can be damaged by many sorts of mutagens , which change
10148-421: The island of Madagascar . The eight species in the family exhibit significant variations in form. These differences initially led to the species in this family sharing common names with, and being placed in the different families of, apparently more similar species on the mainland (e.g. civets and mongoose). However, phylogenetic analysis of DNA provides strong evidence that all Malagasy carnivorans evolved from
10266-543: The larger males weighing up to 5 kg (11 lb). Family Prionodontidae ( Asiatic linsangs ) has two extant species in one genus. They live in Southern-East Asia. All are arboreal hypercarnivorans . They are the closest living relatives of the family Felidae. Family Viverridae (all but two civets , genets , oyans , and the binturong ) has 30 living species. They all have long bodies, short legs with retractile claws, and usually long tails. In weight,
10384-407: The limbs have been modified into flippers . Unlike cetaceans and sirenians , which have fully functional tails to help them swim, pinnipeds use their limbs underwater to swim. Earless seals use their back flippers; sea lions and fur seals use their front flippers, and the walrus uses all of its limbs. As a result, pinnipeds have significantly shorter tails than other carnivorans. Aside from
10502-536: The methods in which mammalogists use to assess the phylogenetic relationships among the carnivoran families has been improved with using more complicated and intensive incorporation of genetics, morphology and the fossil record. Research into Carnivora phylogeny since 1945 has found Fisspedia to be paraphyletic in respect to Pinnipedia, with pinnipeds being either more closely related to bears or to weasels. The small carnivoran families Viverridae, Procyonidae, and Mustelidae have been found to be polyphyletic : Below
10620-401: The miacids, with a full complement of molars, and the viverravines with a reduced number of molars and more specialized carnassials. These dental differences resemble the difference between Caniforms (with more teeth) and Feliforms (with fewer teeth) but this may not mean evolutionary lineages. It was thought that Viverravidae was basal to the Feliforms. However, some studies suggest this is not
10738-441: The minor groove is 12 Å (1.2 nm) in width. Due to the larger width of the major groove, the edges of the bases are more accessible in the major groove than in the minor groove. As a result, proteins such as transcription factors that can bind to specific sequences in double-stranded DNA usually make contact with the sides of the bases exposed in the major groove. This situation varies in unusual conformations of DNA within
10856-516: The mitochondrial genome (constituting up to 90% of the DNA of the cell). A DNA sequence is called a "sense" sequence if it is the same as that of a messenger RNA copy that is translated into protein. The sequence on the opposite strand is called the "antisense" sequence. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands can contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but
10974-477: The most dangerous are double-strand breaks, as these are difficult to repair and can produce point mutations , insertions , deletions from the DNA sequence, and chromosomal translocations . These mutations can cause cancer . Because of inherent limits in the DNA repair mechanisms, if humans lived long enough, they would all eventually develop cancer. DNA damages that are naturally occurring , due to normal cellular processes that produce reactive oxygen species,
11092-520: The most dominant group of large terrestrial predators in Eurasia and North America, with various lineages being successful in megafaunal faunivorous niches at different intervals during the Miocene and later epochs. The order Carnivora belongs to a group of mammals known as Laurasiatheria , which also includes other groups such as bats and ungulates . Within this group the carnivorans are placed in
11210-429: The most problematic being Nimravidae ). All extant feliforms share a common attribute: their auditory bullae (bony capsules enclosing the middle and inner ear ). This is a key diagnostic in classifying species as feliform versus caniform. In feliforms, the auditory bullae are double-chambered, composed of two bones joined by a septum . Caniforms have single-chambered or partially divided auditory bullae, composed of
11328-442: The nature of the carnassial teeth is different between the two groups. In carnivorans the carnassials are positioned near the front of the molar row, while in the creodonts they are positioned near the back of the molar row, and this suggests a separate evolutionary history and an order-level distinction. In addition, recent phylogenetic analysis suggests that creodonts are more closely related to pangolins while mesonychians might be
11446-464: The new strand, and the cell ends up with a perfect copy of its DNA. Naked extracellular DNA (eDNA), most of it released by cell death, is nearly ubiquitous in the environment. Its concentration in soil may be as high as 2 μg/L, and its concentration in natural aquatic environments may be as high at 88 μg/L. Various possible functions have been proposed for eDNA: it may be involved in horizontal gene transfer ; it may provide nutrients; and it may act as
11564-800: The only exception, occurring in the old world and the new world, entering the Americas via the Bering Land Bridge. The caniforms include the Caninae , Procyonidae , bears , mustelids , skunks and pinnipeds that occur worldwide with immense diversity in their morphology, diet and behavior. The word carnivore is derived from Latin carō (stem carn- ) 'flesh' and vorāre 'to devour', and refers to any meat-eating organism. The oldest known carnivoran line mammals ( Carnivoramorpha ) appeared in North America 6 million years after
11682-454: The open reading frame. In many species , only a small fraction of the total sequence of the genome encodes protein. For example, only about 1.5% of the human genome consists of protein-coding exons , with over 50% of human DNA consisting of non-coding repetitive sequences . The reasons for the presence of so much noncoding DNA in eukaryotic genomes and the extraordinary differences in genome size , or C-value , among species, represent
11800-783: The pinnipeds, dogs, bears, hyenas, and cats all have distinct and recognizable appearances. Dogs are usually cursorial mammals and are gracile in appearance, often relying on their teeth to hold prey; bears are much larger and rely on their physical strength to forage for food. Compared to dogs and bears, cats have longer and stronger forelimbs armed with retractable claws to hold on to prey. Hyenas are dog-like feliforms that have sloping backs due to their front legs being longer than their hind legs. The raccoon family and red panda are small, bear-like carnivorans with long tails. The other small carnivoran families Nandiniidae , Prionodontidae , Viverridae , Herpestidae , Eupleridae, Mephitidae and Mustelidae have through convergent evolution maintained
11918-428: The place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. In addition to RNA and DNA, many artificial nucleic acid analogues have been created to study the properties of nucleic acids, or for use in biotechnology. Modified bases occur in DNA. The first of these recognized was 5-methylcytosine , which was found in the genome of Mycobacterium tuberculosis in 1925. The reason for
12036-530: The presence of these noncanonical bases in bacterial viruses ( bacteriophages ) is to avoid the restriction enzymes present in bacteria. This enzyme system acts at least in part as a molecular immune system protecting bacteria from infection by viruses. Modifications of the bases cytosine and adenine, the more common and modified DNA bases, play vital roles in the epigenetic control of gene expression in plants and animals. A number of noncanonical bases are known to occur in DNA. Most of these are modifications of
12154-412: The prime symbol being used to distinguish these carbon atoms from those of the base to which the deoxyribose forms a glycosidic bond . Therefore, any DNA strand normally has one end at which there is a phosphate group attached to the 5′ carbon of a ribose (the 5′ phosphoryl) and another end at which there is a free hydroxyl group attached to the 3′ carbon of a ribose (the 3′ hydroxyl). The orientation of
12272-466: The proposals was the existence of lifeforms that use arsenic instead of phosphorus in DNA . A report in 2010 of the possibility in the bacterium GFAJ-1 was announced, though the research was disputed, and evidence suggests the bacterium actively prevents the incorporation of arsenic into the DNA backbone and other biomolecules. At the ends of the linear chromosomes are specialized regions of DNA called telomeres . The main function of these regions
12390-432: The section on uses in technology below. Several artificial nucleobases have been synthesized, and successfully incorporated in the eight-base DNA analogue named Hachimoji DNA . Dubbed S, B, P, and Z, these artificial bases are capable of bonding with each other in a predictable way (S–B and P–Z), maintain the double helix structure of DNA, and be transcribed to RNA. Their existence could be seen as an indication that there
12508-431: The sequence of amino acids within proteins in a process called translation . Within eukaryotic cells, DNA is organized into long structures called chromosomes . Before typical cell division , these chromosomes are duplicated in the process of DNA replication, providing a complete set of chromosomes for each daughter cell. Eukaryotic organisms ( animals , plants , fungi and protists ) store most of their DNA inside
12626-476: The shape of a double helix . The nucleotide contains both a segment of the backbone of the molecule (which holds the chain together) and a nucleobase (which interacts with the other DNA strand in the helix). A nucleobase linked to a sugar is called a nucleoside , and a base linked to a sugar and to one or more phosphate groups is called a nucleotide . A biopolymer comprising multiple linked nucleotides (as in DNA)
12744-552: The single-ringed pyrimidines and the double-ringed purines . In DNA, the pyrimidines are thymine and cytosine; the purines are adenine and guanine. Both strands of double-stranded DNA store the same biological information . This information is replicated when the two strands separate. A large part of DNA (more than 98% for humans) is non-coding , meaning that these sections do not serve as patterns for protein sequences . The two strands of DNA run in opposite directions to each other and are thus antiparallel . Attached to each sugar
12862-502: The single-stranded DNA curls around in a long circle stabilized by telomere-binding proteins. At the very end of the T-loop, the single-stranded telomere DNA is held onto a region of double-stranded DNA by the telomere strand disrupting the double-helical DNA and base pairing to one of the two strands. This triple-stranded structure is called a displacement loop or D-loop . In DNA, fraying occurs when non-complementary regions exist at
12980-408: The sister group to carnivorans and their stem-relatives. The closest stem-carnivorans are the miacoids . The miacoids include the families Viverravidae and Miacidae , and together the Carnivora and Miacoidea form the stem-clade Carnivoramorpha . The miacoids were small, genet-like carnivoramorphs that occupy a variety of niches such as terrestrial and arboreal habitats. Recent studies have shown
13098-406: The small, ancestral appearance of the miacoids, though there is some variation seen such as the robust and stout physicality of badgers and the wolverine ( Gulo gulo ). Most carnivoran species have a well-defined breeding season . Male carnivorans usually have bacula , which are absent in hyenas and binturongs . The length and density of the fur vary depending on the environment that
13216-433: The species inhabits. In warm climate species, the fur is often short in length and lighter. In cold climate species, the fur is either dense or long, often with an oily substance that helps to retain heat. The pelage coloration differs between species, often including black, white, orange, yellow, red, and many shades of grey and brown. Some are striped, spotted, blotched, banded, or otherwise boldly patterned. There seems to be
13334-781: The species range from 0.5–14 kg (1.1–30.9 lb). Some occur in Southern Europe, but most in Africa and Asia. Their diet ranges from fruit and plants to insects, crustaceans and molluscs , and small mammals. In the Middle Palaeocene (60 million years ago), Miacoidea appears. Miacoids were a group of paraphyletic taxa believed to be basal to Carnivora. They had Carnivora-like carnassials but lacked fully ossified auditory bullae. Miacids were small arboreal carnivorans and, based on their size (roughly that of mongooses), they probably fed on insects, small mammals and birds. The miacoids are divided into two groups:
13452-495: The species size and available food sources (with the larger species feeding mainly on small mammals and the smallest species feeding on insects or invertebrates ). An overview of each family is provided here. For detailed taxa and descriptions of the species in each family, follow the links to other articles and external references. Family Eupleridae (the "Malagasy carnivorans") includes fossa , falanouc , Malagasy civet and Malagasy mongooses , all of which are restricted to
13570-518: The strands separate and exist in solution as two entirely independent molecules. These single-stranded DNA molecules have no single common shape, but some conformations are more stable than others. In humans, the total female diploid nuclear genome per cell extends for 6.37 Gigabase pairs (Gbp), is 208.23 cm long and weighs 6.51 picograms (pg). Male values are 6.27 Gbp, 205.00 cm, 6.41 pg. Each DNA polymer can contain hundreds of millions of nucleotides, such as in chromosome 1 . Chromosome 1
13688-469: The sugar-phosphate to form the complete nucleotide, as shown for adenosine monophosphate . Adenine pairs with thymine and guanine pairs with cytosine, forming A-T and G-C base pairs . The nucleobases are classified into two types: the purines , A and G , which are fused five- and six-membered heterocyclic compounds , and the pyrimidines , the six-membered rings C and T . A fifth pyrimidine nucleobase, uracil ( U ), usually takes
13806-486: Was not until 1821 that the English writer and traveler Thomas Edward Bowdich gave the group its modern and accepted name. Initially, the modern concept of Carnivora was divided into two suborders: the terrestrial Fissipedia and the marine Pinnipedia . Below is the classification of how the extant families were related to each other after American paleontologist George Gaylord Simpson in 1945: Since then, however,
13924-526: Was proposed by Wilkins et al. in 1953 for the in vivo B-DNA X-ray diffraction-scattering patterns of highly hydrated DNA fibers in terms of squares of Bessel functions . In the same journal, James Watson and Francis Crick presented their molecular modeling analysis of the DNA X-ray diffraction patterns to suggest that the structure was a double helix. Although the B-DNA form is most common under
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