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88-406: Cyclins were originally discovered by R. Timothy Hunt in 1982 while studying the cell cycle of sea urchins. In an interview for "The Life Scientific" (aired on 13/12/2011) hosted by Jim Al-Khalili , R. Timothy Hunt explained that the name "cyclin" was originally named after his hobby cycling. It was only after the naming did its importance in the cell cycle become apparent. As it was appropriate

176-511: A Bachelor of Science degree in 1986. He stayed on at Surrey to pursue a Doctor of Philosophy degree in nuclear reaction theory, which he obtained in 1989, rather than accepting a job offer from the National Physical Laboratory . In 1989, Al-Khalili was awarded a Science and Engineering Research Council (SERC) postdoctoral fellowship at University College London , after which he returned to Surrey in 1991, first as

264-848: A Fellow of the Institute of Physics since 2000, when he also received the Institute's Public Awareness of Physics Award. He has lectured widely both in the UK and around the world, particularly for the British Council . He is a member of the British Council Science and Engineering Advisory Group, a member of the Royal Society Equality and Diversity Panel, an external examiner for the Open University Department of Physics and Astronomy,

352-608: A Horizon special on BBC 2 , which examined the latest scientific developments in the quest to discover the Higgs Boson , with preliminary results from the Large Hadron Collider experiment at CERN suggesting that the elusive particle does indeed exist. Al-Khalili lives in Southsea , Portsmouth , with his wife Julie. They have a son and daughter. Al-Khalili is an atheist and a humanist , remarking, "as

440-417: A lethargus phase occurs shortly before each moult . C. elegans has also been demonstrated to sleep after exposure to physical stress, including heat shock, UV radiation, and bacterial toxins. While the worm has no eyes, it has been found to be sensitive to light due to a third type of light-sensitive animal photoreceptor protein , LITE-1 , which is 10 to 100 times more efficient at absorbing light than

528-469: A model organism . It was the first multicellular organism to have its whole genome sequenced , and in 2019 it was the first organism to have its connectome (neuronal "wiring diagram") completed. Four Nobel prizes have been won (as of 2024) for work done on C. elegans. C.   elegans is unsegmented , vermiform , and bilaterally symmetrical . It has a cuticle (a strong outer covering, as an exoskeleton ), four main epidermal cords, and

616-469: A D-type cyclin (ORF72) that binds CDK6 and is likely to contribute to KSHV-related cancers. Cyclins are generally very different from each other in primary structure, or amino acid sequence. However, all members of the cyclin family are similar in 100 amino acids that make up the cyclin box. Cyclins contain two domains of a similar all-α fold , the first located at the N-terminus and the second at

704-482: A canonical way similar to other eukaryotes, in contrast Drosophila melanogaster is noteworthy in its use of retrotransposons to maintain its telomeres, during knock-out of the catalytic subunit of the telomerase ( trt-1 ) C. elegans can gain the ability of alternative telomere lengthening (ALT). C. elegans was the first eukaryote to gain ALT functionality after knock-out of the canonical telomerase pathway. ALT

792-811: A chair in the Public Engagement in Science. He has been a trustee (2006–2012) and vice president (2008–2011) of the British Science Association . He also held an EPSRC Senior Media Fellowship. Al-Khalili was awarded the Royal Society of London Michael Faraday Prize for science communication for 2007 and elected an Honorary Fellow of the British Association for the Advancement of Science . He has been

880-515: A characteristic dauer cuticle and cannot take in food. They can remain in this stage for a few months. The stage ends when conditions improve favour further growth of the larva, now moulting into the L4 stage, even though the gonad development is arrested at the L2 stage. Each stage transition is punctuated by a molt of the worm's transparent cuticle. Transitions through these stages are controlled by genes of

968-445: A diet of a variety of bacteria, but its wild ecology is largely unknown. Most laboratory strains were taken from artificial environments such as gardens and compost piles . More recently, C. elegans has been found to thrive in other kinds of organic matter, particularly rotting fruit. C. elegans can also ingest pollutants, especially tiny nanoplastics, which could enable the association with antibiotic-resistant bacteria, resulting in

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1056-416: A fluid-filled pseudocoelom (body cavity). It also has some of the same organ systems as larger animals. About one in a thousand individuals is male and the rest are hermaphrodites. The basic anatomy of C.   elegans includes a mouth, pharynx , intestine , gonad , and collagenous cuticle. Like all nematodes, they have neither a circulatory nor a respiratory system. The four bands of muscles that run

1144-415: A general idea of the sex determination pathway in C. elegans , however, the evolution of how this pathway came to be is not yet well defined. The fertilized zygote undergoes rotational holoblastic cleavage . Sperm entry into the oocyte commences formation of an anterior-posterior axis. The sperm microtubule organizing center directs the movement of the sperm pronucleus to the future posterior pole of

1232-430: A half. Similarly, induced degradation of an insulin/IGF-1 receptor late in life extended life expectancy of worms dramatically. Long-lived mutants of C. elegans were demonstrated to be resistant to oxidative stress and UV light . These long-lived mutants had a higher DNA repair capability than wild-type C. elegans . Knockdown of the nucleotide excision repair gene Xpa-1 increased sensitivity to UV and reduced

1320-761: A member of the Editorial Board for the open access Journal PMC Physics A, and Associate Editor of Advanced Science Letters. He is also a member of the Advisory Committee for the Cheltenham Science Festival . In 2007, he was a judge on the BBC Samuel Johnson Prize for non-fiction and has been a celebrity judge at the National Science & Engineering Competition Finals at The Big Bang Fair. He

1408-551: A model organism, any information discovered about the way their sex determination system might have evolved could further the same evolutionary biology research in other organisms. After almost 30 years of research, scientists have begun to put together the pieces in the evolution of such a system. What they have discovered is that there is a complex pathway involved that has several layers of regulation. The closely related organism Caenorhabditis briggsae has been studied extensively and its whole genome sequence has helped put together

1496-682: A presenter came in 2007 with Atom , a three-part series on BBC Four about the history of our understanding of the atom and atomic physics. This was followed by a special archive edition of Horizon , "The Big Bang". In early 2009, Al-Khalili presented the BBC Four three-part series Science and Islam about the leap in scientific knowledge that took place in the Islamic world between the 8th and 14th centuries. He has contributed to programmes ranging from Tomorrow's World , BBC Four's Mind Games , The South Bank Show to BBC One 's Bang Goes

1584-483: A research assistant, then as a lecturer. In 1994, Al-Khalili was awarded an Engineering and Physical Sciences Research Council (EPSRC) Advanced Research Fellowship for five years, during which time he established himself as a leading expert on mathematical models of exotic atomic nuclei . He has published widely in his field. Al-Khalili is a professor of physics at the University of Surrey , where he also holds

1672-411: A single cell-death inhibitor have been identified. RNA interference (RNAi) is a relatively straightforward method of disrupting the function of specific genes. Silencing the function of a gene can sometimes allow a researcher to infer its possible function. The nematode can be soaked in, injected with, or fed with genetically transformed bacteria that express the double-stranded RNA of interest,

1760-399: A wave of contractions is initiated at the front and proceeds posteriorly along the body, the animal is propelled forwards. Because of this dorsal/ventral bias in body bends, any normal living, moving individual tends to lie on either its left side or its right side when observed crossing a horizontal surface. A set of ridges on the lateral sides of the body cuticle, the alae, is believed to give

1848-435: Is a multicellular eukaryotic organism, yet simple enough to be studied in great detail. The transparency of C. elegans facilitates the study of cellular differentiation and other developmental processes in the intact organism. The spicules in the male clearly distinguish males from females. Strains are cheap to breed and can be frozen. When subsequently thawed, they remain viable, allowing long-term storage. Maintenance

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1936-481: Is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a blend of the Greek caeno- (recent), rhabditis (rod-like) and Latin elegans (elegant). In 1900, Maupas initially named it Rhabditides elegans. Osche placed it in the subgenus Caenorhabditis in 1952, and in 1955, Dougherty raised Caenorhabditis to

2024-422: Is a muscular food pump in the head of C.   elegans , which is triangular in cross-section. This grinds food and transports it directly to the intestine. A set of "valve cells" connects the pharynx to the intestine, but how this valve operates is not understood. After digestion, the contents of the intestine are released via the rectum, as is the case with all other nematodes. No direct connection exists between

2112-466: Is also observed in about 10-15% of all clinical cancers. Thus C. elegans is a prime candidate for ALT research. Bayat et al. showed the paradoxical shortening of telomeres during trt-1 over-expression which lead to near sterility while the worms even exhibited a slight increase in lifespan, despite shortened telomeres. C. elegans is notable in animal sleep studies as the most primitive organism to display sleep-like states. In C. elegans ,

2200-438: Is at the same given position as it moves down the gonad, so is at the same stage in meiosis. In an early phase of meiosis, the oocytes become extremely resistant to radiation and this resistance depends on expression of genes rad51 and atm that have key roles in recombinational repair. Gene mre-11 also plays a crucial role in recombinational repair of DNA damage during meiosis. Furthermore, during meiosis in C. elegans

2288-512: Is attributed to the tra-1 gene. The tra-1 is a gene within the TRA-1 transcription factor sex determination pathway that is regulated post-transcriptionally and works by promoting female development. In hermaphrodites (XX), there are high levels of tra-1 activity, which produces the female reproductive system and inhibits male development. At a certain time in their life cycle, one day before adulthood, hermaphrodites can be identified through

2376-500: Is based on an X0 sex-determination system . Hermaphrodites of C. elegans have a matched pair of sex chromosomes (XX); the rare males have only one sex chromosome (X0). C. elegans are mostly hermaphroditic organisms, producing both sperms and oocytes . Males do occur in the population in a rate of approximately 1 in 200 hermaphrodites, but the two sexes are highly differentiated. Males differ from their hermaphroditic counterparts in that they are smaller and can be identified through

2464-412: Is considered to be a specialized form of self-fertile female, as its soma is female. The hermaphroditic germline produces male gametes first, and lays eggs through its uterus after internal fertilization. Hermaphrodites produce all their sperm in the L4 stage (150 sperm cells per gonadal arm) and then produce only oocytes . The hermaphroditic gonad acts as an ovotestis with sperm cells being stored in

2552-541: Is due solely to an increase in the size of individual cells. The different Caenorhabditis species occupy various nutrient- and bacteria-rich environments. They feed on the bacteria that develop in decaying organic matter ( microbivory ). They possess chemosensory receptors which enable the detection of bacteria and bacterial-secreted metabolites (such as iron siderophores), so that they can migrate towards their bacterial prey. Soil lacks enough organic matter to support self-sustaining populations. C. elegans can survive on

2640-426: Is easy when compared to other multicellular model organisms. A few hundred nematodes can be kept on a single agar plate and suitable growth medium. Brenner described the use of a mutant of E. coli – OP50. OP50 is a uracil -requiring organism and its deficiency in the plate prevents the overgrowth of bacteria which would obscure the worms. The use of OP50 does not demand any major laboratory safety measures, since it

2728-535: Is non-pathogenic and easily grown in Luria-Bertani (LB) media overnight. The developmental fate of every single somatic cell (959 in the adult hermaphrodite; 1031 in the adult male) has been mapped. These patterns of cell lineage are largely invariant between individuals, whereas in mammals, cell development is more dependent on cellular cues from the embryo. As mentioned previously, the first cell divisions of early embryogenesis in C. elegans are among

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2816-453: Is professor of theoretical physics and chair in the public engagement in science at the University of Surrey . He is a regular broadcaster and presenter of science programmes on BBC radio and television, and a frequent commentator about science in other British media. In 2014, Al-Khalili was named as a RISE (Recognising Inspirational Scientists and Engineers) leader by the UK's Engineering and Physical Sciences Research Council (EPSRC). He

2904-539: Is unclear exactly when specifically the axis is determined. However, most theories of the L-R axis development involve some kind of differences in cells derived from the AB cell. Gastrulation occurs after the embryo reaches the 24-cell stage. C. elegans are a species of protostomes , so the blastopore eventually forms the mouth. Involution into the blastopore begins with movement of the endoderm cells and subsequent formation of

2992-494: The C-terminus . All cyclins are believed to contain a similar tertiary structure of two compact domains of 5 α helices. The first of which is the conserved cyclin box, outside of which cyclins are divergent. For example, the amino-terminal regions of S and M cyclins contain short destruction-box motifs that target these proteins for proteolysis in mitosis. There are several different cyclins that are active in different parts of

3080-545: The P4 cell, established early in embryogenesis . This primordial cell divides to generate two germline precursors that do not divide further until after hatching. The resulting daughter cells of the first cell division are called the AB cell (containing PAR-6 and PAR-3) and the P1 cell (containing PAR-1 and PAR-2). A second cell division produces the ABp and ABa cells from the AB cell, and

3168-792: The Royal Academy of Engineering in 2023. He was appointed Commander of the Order of the British Empire (CBE) in the 2021 Birthday Honours for services to science and public engagement in STEM . As a broadcaster, Al-Khalili is frequently on television and radio and also writes articles for the British press. In 2004, he co-presented the Channel 4 documentary The Riddle of Einstein's Brain , produced by Icon Films . His big break as

3256-496: The dauer stage ( Dauer is German for permanent). A specific dauer pheromone regulates entry into the dauer state. This pheromone is composed of similar derivatives of the 3,6-dideoxy sugar, ascarylose . Ascarosides, named after the ascarylose base, are involved in many sex-specific and social behaviors. In this way, they constitute a chemical language that C. elegans uses to modulate various phenotypes. Dauer larvae are stress-resistant; they are thin and their mouths are sealed with

3344-422: The life span of the long-lived mutants. These findings indicate that DNA repair capability underlies longevity . The capacity to repair DNA damage by the process of nucleotide excision repair declines with age. C. elegans exposed to 5mM lithium chloride (LiCl) showed lengthened life spans. When exposed to 10μM LiCl, reduced mortality was observed, but not with 1μM. C. elegans has been instrumental in

3432-509: The Cdks to specific subcellular locations. Cyclins, when bound with the dependent kinases , such as the p34 / cdc2 / cdk1 protein, form the maturation-promoting factor . MPFs activate other proteins through phosphorylation . These phosphorylated proteins, in turn, are responsible for specific events during cell division such as microtubule formation and chromatin remodeling . Cyclins can be divided into four classes based on their behaviour in

3520-590: The EMS and P2 cells from the P1 cell. This division establishes the dorsal-ventral axis, with the ABp cell forming the dorsal side and the EMS cell marking the ventral side. Through Wnt signaling , the P2 cell instructs the EMS cell to divide along the anterior-posterior axis. Through Notch signaling , the P2 cell differentially specifies the ABp and ABa cells, which further defines the dorsal-ventral axis. The left-right axis also becomes apparent early in embryogenesis, although it

3608-712: The Theory . In 2010 he presented the BBC documentary on the history of chemistry , Chemistry: A Volatile History . In October 2011, he began a programme on famous contemporary scientists on Radio Four , called The Life Scientific . The first of this series featured his interview with Paul Nurse . He has since interviewed a series of notable scientists, including Richard Dawkins , Alice Roberts , James Lovelock , Steven Pinker , Martin Rees , Jocelyn Bell Burnell , Mark Walport and Tim Hunt , and he has himself been interviewed on

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3696-401: The adaptive benefit of recombinational repair of DNA damages that arise, especially under stressful conditions. Nicotine dependence can also be studied using C. elegans because it exhibits behavioral responses to nicotine that parallel those of mammals. These responses include acute response, tolerance, withdrawal, and sensitization. As for most model organisms, scientists that work in

3784-459: The addition of a vulva near their tail. In males (XO), there are low levels of tra-1 activity, resulting in a male reproductive system. Recent research has shown that there are three other genes, fem-1, fem-2, and fem-3, that negatively regulate the TRA-1 pathway and act as the final determiner of sex in C. elegans . The sex determination system in C. elegans is a topic that has been of interest to scientists for years. Since they are used as

3872-425: The animal added traction during these bending motions. In relation to lipid metabolism, C.   elegans does not have any specialized adipose tissues, a pancreas , a liver , or even blood to deliver nutrients compared to mammals. Neutral lipids are instead stored in the intestine, epidermis, and embryos. The epidermis corresponds to the mammalian adipocytes by being the main triglyceride depot. The pharynx

3960-413: The best understood examples of asymmetric cell divisions , and the worm is a very popular model system for studying developmental biology. Programmed cell death ( apoptosis ) eliminates many additional cells (131 in the hermaphrodite, most of which would otherwise become neurons ); this "apoptotic predictability" has contributed to the elucidation of some apoptotic genes . Cell death-promoting genes and

4048-414: The bi-oriented attachment of chromosomes to spindle microtubules through specialized structures called kinetochores. In the early phases of division, there are numerous errors in how kinetochores bind to spindle microtubules. The unstable attachments promote the correction of errors by causing a constant detachment, realignment and reattachment of microtubules from kinetochores in the cells as they try to find

4136-452: The body cavity of the animal induces gene silencing in most species, only C. elegans and a few other distantly related nematodes can take up RNA from the bacteria they eat for RNAi. This ability has been mapped down to a single gene, sid-2 , which, when inserted as a transgene in other species, allows them to take up RNA for RNAi as C. elegans does. Research into meiosis has been considerably simplified since every germ cell nucleus

4224-668: The cell cycle and that cause the Cdk to phosphorylate different substrates. There are also several "orphan" cyclins for which no Cdk partner has been identified. For example, cyclin F is an orphan cyclin that is essential for G 2 /M transition. A study in C. elegans revealed the specific roles of mitotic cyclins. Notably, recent studies have shown that cyclin A creates a cellular environment that promotes microtubule detachment from kinetochores in prometaphase to ensure efficient error correction and faithful chromosome segregation. Cells must separate their chromosomes precisely, an event that relies on

4312-592: The cell cycle of vertebrate somatic cells and yeast cells: G1 cyclins, G1/S cyclins, S cyclins, and M cyclins. This division is useful when talking about most cell cycles, but it is not universal as some cyclins have different functions or timing in different cell types. G1/S Cyclins rise in late G1 and fall in early S phase. The Cdk- G1/S cyclin complex begins to induce the initial processes of DNA replication, primarily by arresting systems that prevent S phase Cdk activity in G1. The cyclins also promote other activities to progress

4400-436: The cell cycle, such as centrosome duplication in vertebrates or spindle pole body in yeast. The rise in presence of G1/S cyclins is paralleled by a rise in S cyclins. G1 cyclins do not behave like the other cyclins, in that the concentrations increase gradually (with no oscillation), throughout the cell cycle based on cell growth and the external growth-regulatory signals. The presence of G cyclins coordinate cell growth with

4488-507: The cell cycle.) The oscillations of the cyclins, namely fluctuations in cyclin gene expression and destruction by the ubiquitin mediated proteasome pathway, induce oscillations in Cdk activity to drive the cell cycle. A cyclin forms a complex with Cdk, which begins to activate, but the complete activation requires phosphorylation as well. Complex formation results in activation of the Cdk active site . Cyclins themselves have no enzymatic activity but have binding sites for some substrates and target

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4576-475: The cell to receive neurotransmitters or other signals, and a process that extends to the nerve ring (the "brain") for a synaptic connection with other neurons. C.   elegans has excitatory cholinergic and inhibitory GABAergic motor neurons which connect with body wall muscles to regulate movement. In addition, these neurons and other neurons such as interneurons use a variety of neurotransmitters to control behaviors. Numerous gut granules are present in

4664-410: The connectome of the male was published using a technique distinct from that used for the hermaphrodite. The same paper used the new technique to redo the hermaphrodite connectome, finding 1,500 new synapses. It has been used as a model organism to study molecular mechanisms in metabolic diseases. Brenner also chose it as it is easy to grow in bulk populations, and convenient for genetic analysis. It

4752-825: The correct attachment. Protein cyclin A governs this process by keeping the process going until the errors are eliminated. In normal cells, persistent cyclin A expression prevents the stabilization of microtubules bound to kinetochores even in cells with aligned chromosomes. As levels of cyclin A decline, microtubule attachments become stable, allowing the chromosomes to be divided correctly as cell division proceeds. In contrast, in cyclin A-deficient cells, microtubule attachments are prematurely stabilized. Consequently, these cells may fail to correct errors, leading to higher rates of chromosome mis-segregation. There are two main groups of cyclins: The specific cyclin subtypes along with their corresponding CDK (in brackets) are: In addition,

4840-937: The dissemination of nanoplastics and antibiotic-resistant bacteria by C. elegans across the soil. C. elegans can also use different species of yeast , including Cryptococcus laurentii and C. kuetzingii , as sole sources of food. Although a bacterivore , C. elegans can be killed by a number of pathogenic bacteria, including human pathogens such as Staphylococcus aureus , Pseudomonas aeruginosa , Salmonella enterica or Enterococcus faecalis . Pathogenic bacteria can also form biofilms, whose sticky exopolymer matrix could impede C. elegans motility and cloaks bacterial quorum sensing chemoattractants from predator detection. Invertebrates such as millipedes , insects , isopods , and gastropods can transport dauer larvae to various suitable locations. The larvae have also been seen to feed on their hosts when they die. Nematodes can survive desiccation , and in C. elegans ,

4928-483: The embryo, while also inciting the movement of PAR proteins , a group of cytoplasmic determination factors, to their proper respective locations. As a result of the difference in PAR protein distribution, the first cell division is highly asymmetric . C. elegans embryogenesis is among the best understood examples of asymmetric cell division. All cells of the germline arise from a single primordial germ cell , called

5016-466: The entry to a new cell cycle. S cyclins bind to Cdk and the complex directly induces DNA replication. The levels of S cyclins remain high, not only throughout S phase, but through G2 and early mitosis as well to promote early events in mitosis. M cyclin concentrations rise as the cell begins to enter mitosis and the concentrations peak at metaphase. Cell changes in the cell cycle like the assembly of mitotic spindles and alignment of sister-chromatids along

5104-641: The field curate a dedicated online database and WormBase is that for C. elegans . The WormBase attempts to collate all published information on C. elegans and other related nematodes. Information on C. elegans is included with data on other model organisms in the Alliance of Genome Resources. C. elegans has been a model organism for research into ageing ; for example, the inhibition of an insulin-like growth factor signaling pathway has been shown to increase adult lifespan threefold; while glucose feeding promotes oxidative stress and reduces adult lifespan by

5192-492: The following human protein contains a cyclin domain: CNTD1 Leland H. Hartwell , R. Timothy Hunt , and Paul M. Nurse won the 2001 Nobel Prize in Physiology or Medicine for their discovery of cyclin and cyclin-dependent kinase. Jim Al-Khalili Jameel Sadik " Jim " Al-Khalili ( Arabic : جميل صادق الخليلي ; born 20 September 1962 ) is an Iraqi-British theoretical physicist and science populariser. He

5280-603: The gut, followed by the P4 germline precursor, and finally the mesoderm cells, including the cells that eventually form the pharynx. Gastrulation ends when epiboly of the hypoblasts closes the blastopore. Under environmental conditions favourable for reproduction , hatched larvae develop through four larval stages - L1, L2, L3, and L4 - in just 3 days at 20 °C. When conditions are stressed, as in food insufficiency, excessive population density or high temperature, C. elegans can enter an alternative third larval stage, L2d, called

5368-414: The hermaphrodite, this system comprises 302 neurons the pattern of which has been comprehensively mapped, in what is known as a connectome , and shown to be a small-world network . Research has explored the neural and molecular mechanisms that control several behaviors of C. elegans , including chemotaxis , thermotaxis , mechanotransduction , learning , memory , and mating behaviour. In 2019

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5456-405: The heterochronic pathway, an evolutionarily conserved set of regulatory factors. Many heterochronic genes code for microRNAs , which repress the expression of heterochronic transcription factors and other heterochronic miRNAs. miRNAs were originally discovered in C. elegans. Important developmental events controlled by heterochronic genes include the division and eventual syncitial fusion of

5544-437: The hypodermic seam cells, and their subsequent secretion of the alae in young adults. It is believed that the heterochronic pathway represents an evolutionarily conserved predecessor to circadian clocks . Some nematodes have a fixed, genetically determined number of cells, a phenomenon known as eutely . The adult C. elegans hermaphrodite has 959 somatic cells and the male has 1033 cells, although it has been suggested that

5632-590: The identification of the functions of genes implicated in Alzheimer's disease , such as presenilin . Moreover, extensive research on C. elegans has identified RNA-binding proteins as essential factors during germline and early embryonic development. Telomeres , the length of which have been shown to correlate with increased lifespan and delayed onset of senescence in a multitude of organisms, from C. elegans to humans, show an interesting behaviour in C. elegans. While C. elegans maintains its telomeres in

5720-460: The intestine of C.   elegans , the functions of which are still not fully known, as are many other aspects of this nematode, despite the many years that it has been studied. These gut granules are found in all of the Rhabditida orders. They are very similar to lysosomes in that they feature an acidic interior and the capacity for endocytosis , but they are considerably larger, reinforcing

5808-455: The intestine, and is seen in both young and old worms, whether subjected to lethal injury or peacefully dying of old age. Many theories have been posited on the functions of the gut granules, with earlier ones being eliminated by later findings. They are thought to store zinc as one of their functions. Recent chemical analysis has identified the blue fluorescent material they contain as a glycosylated form of anthranilic acid (AA). The need for

5896-507: The intestines of C. elegans . Arthrobotrys oligospora is the model organism for interactions between fungi and nematodes. It is the most common and widespread nematode capturing fungus. In 1963, Sydney Brenner proposed using C. elegans as a model organism for the investigation primarily of neural development in animals. It is one of the simplest organisms with a nervous system . The neurons do not fire action potentials , and do not express any voltage-gated sodium channels . In

5984-491: The large amounts of AA the many gut granules contain is questioned. One possibility is that the AA is antibacterial and used in defense against invading pathogens. Another possibility is that the granules provide photoprotection; the bursts of AA fluorescence entail the conversion of damaging UV light to relatively harmless visible light. This is seen as a possible link to the melanin –containing melanosomes . The hermaphroditic worm

6072-407: The length of the body are connected to a neural system that allows the muscles to move the animal's body only as dorsal bending or ventral bending, but not left or right, except for the head, where the four muscle quadrants are wired independently from one another. When a wave of dorsal/ventral muscle contractions proceeds from the back to the front of the animal, the animal is propelled backwards. When

6160-600: The mechanism for this capability has been demonstrated to be late embryogenesis abundant proteins . C. elegans , as other nematodes, can be eaten by predator nematodes and other omnivores, including some insects. The Orsay virus is a virus that affects C. elegans , as well as the Caenorhabditis elegans Cer1 virus and the Caenorhabditis elegans Cer13 virus . Wild isolates of Caenorhabditis elegans are regularly found with infections by Microsporidia fungi. One such species, Nematocida parisii , replicates in

6248-489: The missing pieces in the evolution of C. elegans sex determination. It has been discovered that two genes have assimilated, leading to the proteins XOL-1 and MIX-1 having an effect on sex determination in C. elegans as well. Mutations in the XOL-1 pathway leads to feminization in C. elegans . The mix-1 gene is known to hypoactivate the X chromosome and regulates the morphology of the male tail in C. elegans. Looking at

6336-444: The name stuck. R. Timothy Hunt : "By the way, the name cyclin, which I coined, was really a joke, it's because I liked cycling so much at the time, but they did come and go in the cell..." Cyclins were originally named because their concentration varies in a cyclical fashion during the cell cycle. (Note that the cyclins are now classified according to their conserved cyclin box structure, and not all these cyclins alter in level through

6424-505: The nematode as a whole, the male and hermaphrodite sex likely evolved from parallel evolution. Parallel evolution is defined as similar traits evolving from an ancestor in similar conditions; simply put, the two species evolve in similar ways over time. An example of this would be marsupial and placental mammals. Scientists have also hypothesized that hermaphrodite asexual reproduction, or "selfing", could have evolved convergently by studying species similar to C. elegans Other studies on

6512-400: The number of their intestinal cells can increase by one to three in response to gut microbes experienced by mothers. Much of the literature describes the cell number in males as 1031, but the discovery of a pair of left and right MCM neurons increased the number by two in 2015. The number of cells does not change after cell division ceases at the end of the larval period, and subsequent growth

6600-461: The pharynx and the excretory canal, which functions in the release of liquid urine. Males have a single-lobed gonad, a vas deferens , and a tail specialized for mating, which incorporates spicules . Hermaphrodites have two ovaries , oviducts , and spermatheca , and a single uterus . There are 302 neurons in C.   elegans, approximately one-third of all the somatic cells in the whole body. Many neurons contain dendrites which extend from

6688-413: The same area of the gonad as the oocytes until the first oocyte pushes the sperm into the spermatheca (a chamber wherein the oocytes become fertilized by the sperm). The male can inseminate the hermaphrodite, which will preferentially use male sperm (both types of sperm are stored in the spermatheca). The sperm of C. elegans is amoeboid, lacking flagella and acrosomes . When self-inseminated,

6776-433: The sequence of which complements the sequence of the gene that the researcher wishes to disable. RNAi has emerged as a powerful tool in the study of functional genomics. C. elegans has been used to analyse gene functions and claim the promise of future findings in the systematic genetic interactions. Environmental RNAi uptake is much worse in other species of worms in the genus Caenorhabditis . Although injecting RNA into

6864-487: The sex determination evolution suggest that genes involving sperm evolve at the faster rate than female genes. However, sperm genes on the X chromosome have reduced evolution rates. Sperm genes have short coding sequences, high codon bias, and disproportionate representation among orphan genes . These characteristics of sperm genes may be the reason for their high rates of evolution and may also suggest how sperm genes evolved out of hermaphrodite worms. Overall, scientists have

6952-571: The shape of their tail. C.elegans reproduce through a process called androdioecy . This means that they can reproduce in two ways: either through self-fertilization in hermaphrodites or through hermaphrodites breeding with males. Males are produced through non-disjunction of the X chromosomes during meiosis. The worms that reproduce through self-fertilization are at risk for high linkage disequilibrium , which leads to lower genetic diversity in populations and an increase in accumulation of deleterious alleles. In C. elegans , somatic sex determination

7040-460: The show by Adam Rutherford . Al-Khalili hosts a regular "Jim meets..." interview series at the University of Surrey , which is published on the university's YouTube channel. Guests have included David Attenborough , Robert Winston , Brian Cox and Rowan Williams , Archbishop of Canterbury . In 2011, Al-Khalili hosted a three-part documentary series on BBC Four entitled Shock and Awe: The Story of Electricity . In 2012, Al-Khalili presented

7128-751: The son of a Protestant Christian mother and a Shia Muslim father, I have nevertheless ended up without a religious bone in my body". Al-Khalili became vice president of Humanists UK in 2016 after stepping down as its president. He is also a patron of Guildford-based educational, cultural and social community hub, The Guildford Institute. A list of Jim Al-Khalili's peer reviewed research papers can be found on Google Scholar and Scopus . His published books include: His essays, chapters and other contributions include: Jim Al-Khalili has written one science fiction novel: Caenorhabditis elegans Caenorhabditis elegans ( / ˌ s iː n oʊ r æ b ˈ d aɪ t ə s ˈ ɛ l ə ɡ æ n s / )

7216-584: The spindles are induced by M cyclin- Cdk complexes. The destruction of M cyclins during metaphase and anaphase, after the Spindle Assembly Checkpoint is satisfied, causes the exit of mitosis and cytokinesis. Expression of cyclins detected immunocytochemically in individual cells in relation to cellular DNA content (cell cycle phase), or in relation to initiation and termination of DNA replication during S-phase, can be measured by flow cytometry . Kaposi sarcoma herpesvirus ( KSHV ) encodes

7304-499: The status of genus . C. elegans is an unsegmented pseudocoelomate and lacks respiratory or circulatory systems. Most of these nematodes are hermaphrodites and a few are males. Males have specialised tails for mating that include spicules . In 1963, Sydney Brenner proposed research into C. elegans, primarily in the area of neuronal development. In 1974, he began research into the molecular and developmental biology of C. elegans , which has since been extensively used as

7392-533: The tumor suppressor BRCA1 /BRC-1 and the structural maintenance of chromosomes SMC5 / SMC6 protein complex interact to promote high fidelity repair of DNA double-strand breaks . A study of the frequency of outcrossing in natural populations showed that selfing is the predominant mode of reproduction in C. elegans , but that infrequent outcrossing events occur at a rate around 1%. Meioses that result in selfing are unlikely to contribute significantly to beneficial genetic variability, but these meioses may provide

7480-413: The view of their being storage organelles. A particular feature of the granules is that when they are observed under ultraviolet light , they react by emitting an intense blue fluorescence . Another phenomenon seen is termed 'death fluorescence'. As the worms die, a dramatic burst of blue fluorescence is emitted. This death fluorescence typically takes place in an anterior to posterior wave that moves along

7568-409: The wild-type worm lays about 300 eggs. When inseminated by a male, the number of progeny can exceed 1,000. Hermaphrodites do not typically mate with other hermaphrodites. At 20 °C, the laboratory strain of C. elegans (N2) has an average lifespan around 2–3 weeks and a generation time of 3 to 4 days. C. elegans has five pairs of autosomes and one pair of sex chromosomes . Sex in C. elegans

7656-539: Was President of Humanists UK between January 2013 and January 2016. Al-Khalili was born in Baghdad in 1962. His father was an Iraqi Air Force engineer, and his English mother was a librarian. Al-Khalili settled permanently in the United Kingdom in 1979. After completing (and retaking) his A-levels over three years until 1982, he studied physics at the University of Surrey and graduated with

7744-640: Was appointed Officer of the Order of the British Empire (OBE) in the 2008 Birthday Honours . In 2012, he delivered the Gifford Lectures on Alan Turing: Legacy of a Code Breaker at the University of Edinburgh . In 2013 he was awarded an Honorary Degree (DSc) from the University of London. Al-Khalili was elected as a Fellow of the Royal Society in 2018 and elected an Honorary Fellow of

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