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110-709: Galls develop on various plant organs, providing nutrition and shelter to inducing insects. Galls display vast variation in morphology , size, and wall composition. The size of insect galls can range significantly, from approximately two inches in diameter to less than one-sixteenth of an inch. Some galls are so small that they are merely slightly thickened patches on leaves. Their shape can range from spherical to bursiform, bullet-shaped, flower-shaped, cylindrical, or diamond-like. Factors influencing gall morphology include plant species, tissue type, gall-inducing agent, and environmental conditions. They typically exhibit symmetrical forms, although their end shapes vary due to differences in

220-429: A helical structure (i.e., shaped like a corkscrew). Their double-helix model had two strands of DNA with the nucleotides pointing inward, each matching a complementary nucleotide on the other strand to form what look like rungs on a twisted ladder. This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for replication : if

330-534: A sexual process for transferring DNA from one cell to another cell (usually of the same species). Transformation requires the action of numerous bacterial gene products , and its primary adaptive function appears to be repair of DNA damages in the recipient cell. The diploid nature of chromosomes allows for genes on different chromosomes to assort independently or be separated from their homologous pair during sexual reproduction wherein haploid gametes are formed. In this way new combinations of genes can occur in

440-582: A DNA molecule. In 1983, Kary Banks Mullis developed the polymerase chain reaction , providing a quick way to isolate and amplify a specific section of DNA from a mixture. The efforts of the Human Genome Project , Department of Energy, NIH, and parallel private efforts by Celera Genomics led to the sequencing of the human genome in 2003. At its most fundamental level, inheritance in organisms occurs by passing discrete heritable units, called genes , from parents to offspring. This property

550-445: A chemical shock. The osmotic changes that occur as a result are characterized by increased quantities of osmotically active material and induce the cell metaplasia and gall formation. When the chemical shock is of high intensity, metaplasia does not occur. Instead, the plant cells local to the shock die, thereby rejecting the insect and defending the plant tissue. Galls are rich in resins and tannic acid and have been used widely in

660-493: A complex trait is called heritability . Measurement of the heritability of a trait is relative—in a more variable environment, the environment has a bigger influence on the total variation of the trait. For example, human height is a trait with complex causes. It has a heritability of 89% in the United States. In Nigeria, however, where people experience a more variable access to good nutrition and health care , height has

770-483: A different parent. Many species have so-called sex chromosomes that determine the sex of each organism. In humans and many other animals, the Y chromosome contains the gene that triggers the development of the specifically male characteristics. In evolution, this chromosome has lost most of its content and also most of its genes, while the X chromosome is similar to the other chromosomes and contains many genes. This being said, Mary Frances Lyon discovered that there

880-546: A diploid cell with paired chromosomes. Diploid organisms form haploids by dividing, without replicating their DNA, to create daughter cells that randomly inherit one of each pair of chromosomes. Most animals and many plants are diploid for most of their lifespan, with the haploid form reduced to single cell gametes such as sperm or eggs . Although they do not use the haploid/diploid method of sexual reproduction, bacteria have many methods of acquiring new genetic information. Some bacteria can undergo conjugation , transferring

990-509: A famous debate , which is said to exemplify the two major deviations in biological thinking at the time – whether animal structure was due to function or evolution. Most taxa differ morphologically from other taxa. Typically, closely related taxa differ much less than more distantly related ones, but there are exceptions to this. Cryptic species are species which look very similar, or perhaps even outwardly identical, but are reproductively isolated. Conversely, sometimes unrelated taxa acquire

1100-429: A gene is used to produce a specific amino acid sequence . This process begins with the production of an RNA molecule with a sequence matching the gene's DNA sequence, a process called transcription . This messenger RNA molecule then serves to produce a corresponding amino acid sequence through a process called translation . Each group of three nucleotides in the sequence, called a codon , corresponds either to one of

1210-482: A heritability of only 62%. The molecular basis for genes is deoxyribonucleic acid (DNA). DNA is composed of deoxyribose (sugar molecule), a phosphate group, and a base (amine group). There are four types of bases: adenine (A), cytosine (C), guanine (G), and thymine (T). The phosphates make phosphodiester bonds with the sugars to make long phosphate-sugar backbones. Bases specifically pair together (T&A, C&G) between two backbones and make like rungs on

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1320-435: A higher body temperature. In a low-temperature environment, however, the protein's structure is stable and produces dark-hair pigment normally. The protein remains functional in areas of skin that are colder—such as its legs, ears, tail, and face—so the cat has dark hair at its extremities. Environment plays a major role in effects of the human genetic disease phenylketonuria . The mutation that causes phenylketonuria disrupts

1430-506: A ladder. The bases, phosphates, and sugars together make a nucleotide that connects to make long chains of DNA. Genetic information exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain. These chains coil into a double a-helix structure and wrap around proteins called Histones which provide the structural support. DNA wrapped around these histones are called chromosomes. Viruses sometimes use

1540-505: A living cell or organism may increase or decrease gene transcription. A classic example is two seeds of genetically identical corn, one placed in a temperate climate and one in an arid climate (lacking sufficient waterfall or rain). While the average height the two corn stalks could grow to is genetically determined, the one in the arid climate only grows to half the height of the one in the temperate climate due to lack of water and nutrients in its environment. The word genetics stems from

1650-424: A nutritive cellular layer. In a general gall wasp gall, the outermost layer is the epidermis followed by outer cortex and then inner cortex. In some galls these two cortex layers are separated by a lignified layer. The innermost part of a gall is the larval chamber. The nutritive layer is situated between the larval chamber and the inner cortex. There is a nutritional gradient (high to low) from inside to outside of

1760-456: A phenotype involves studying identical and fraternal twins , or other siblings of multiple births . Identical siblings are genetically the same since they come from the same zygote. Meanwhile, fraternal twins are as genetically different from one another as normal siblings. By comparing how often a certain disorder occurs in a pair of identical twins to how often it occurs in a pair of fraternal twins, scientists can determine whether that disorder

1870-604: A range of colors (red, green, yellow, and black). Different taxonomic groups of gall inducers vary in the complexity and diversity of gall formation and organization, with insect induced galls generally being more complex and diverse. Additionally, gall frequency varies based on factors such as weather, plant susceptibility, and pest populations. There are four stages of gall development: initiation, growth and differentiation, maturation, and dehiscence. Gall tissues are nutritive and present high concentrations of lipids, proteins, nitrogen, and other nutrients. The formation of galls which

1980-641: A range of colors (red, green, yellow, and black). Different taxonomic groups of gall inducers vary in the complexity and diversity of gall formation and organization, with insect induced galls generally being more complex and diverse. Additionally, gall frequency varies based on factors such as weather, plant susceptibility, and pest populations. There are four stages of gall development: initiation, growth and differentiation, maturation, and dehiscence. Gall tissues are nutritive and present high concentrations of lipids, proteins, nitrogen, and other nutrients. The formation of galls begins with insect saliva on plants inducing

2090-403: A series of genes can be combined to form a linear linkage map that roughly describes the arrangement of the genes along the chromosome. Genes express their functional effect through the production of proteins, which are molecules responsible for most functions in the cell. Proteins are made up of one or more polypeptide chains, each composed of a sequence of amino acids . The DNA sequence of

2200-485: A shipment of galls from Suwaydiyya near Antioch fetching the high price of 4½ dinars per 100 pounds. The primary use of the galls was as a mordant for black dyes; they were also used to make a high-quality ink . The gall was also used as a medication to treat fever and intestinal ailments. Morphology (biology) Morphology in biology is the study of the form and structure of organisms and their specific structural features. This includes aspects of

2310-529: A similar appearance as a result of convergent evolution or even mimicry . In addition, there can be morphological differences within a species, such as in Apoica flavissima where queens are significantly smaller than workers. A further problem with relying on morphological data is that what may appear morphologically to be two distinct species may in fact be shown by DNA analysis to be a single species. The significance of these differences can be examined through

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2420-457: A single parent. Offspring that are genetically identical to their parents are called clones . Eukaryotic organisms often use sexual reproduction to generate offspring that contain a mixture of genetic material inherited from two different parents. The process of sexual reproduction alternates between forms that contain single copies of the genome ( haploid ) and double copies ( diploid ). Haploid cells fuse and combine genetic material to create

2530-448: A small circular piece of DNA to another bacterium. Bacteria can also take up raw DNA fragments found in the environment and integrate them into their genomes, a phenomenon known as transformation . These processes result in horizontal gene transfer , transmitting fragments of genetic information between organisms that would be otherwise unrelated. Natural bacterial transformation occurs in many bacterial species, and can be regarded as

2640-400: A smooth blend of traits from their parents. Mendel's work provided examples where traits were definitely not blended after hybridization, showing that traits are produced by combinations of distinct genes rather than a continuous blend. Blending of traits in the progeny is now explained by the action of multiple genes with quantitative effects . Another theory that had some support at that time

2750-452: A transition of heredity from its status as myth to that of a scientific discipline, by providing a fundamental theoretical basis for genetics in the twentieth century. Other theories of inheritance preceded Mendel's work. A popular theory during the 19th century, and implied by Charles Darwin 's 1859 On the Origin of Species , was blending inheritance : the idea that individuals inherit

2860-412: A unique three-dimensional structure for that protein, and the three-dimensional structures of proteins are related to their functions. Some are simple structural molecules, like the fibers formed by the protein collagen . Proteins can bind to other proteins and simple molecules, sometimes acting as enzymes by facilitating chemical reactions within the bound molecules (without changing the structure of

2970-400: A variety of hereditary characteristics that replicate and remain active throughout generations. While haploid organisms have only one copy of each chromosome, most animals and many plants are diploid , containing two of each chromosome and thus two copies of every gene. The two alleles for a gene are located on identical loci of the two homologous chromosomes , each allele inherited from

3080-534: A wild rice, produces an edible gall highly valued as a food source in the Zhejiang and Jiangsu provinces of China. Gall-causing bacteria include Agrobacterium tumefaciens and Pseudomonas savastanoi . Gall forming virus was found on rice plants in central Thailand in 1979 and named rice gall dwarf. Symptoms consisted of gall formation along leaf blades and sheaths, dark green discoloration, twisted leaf tips, and reduced numbers of tillers. Some plants died in

3190-488: Is X-chromosome inactivation during reproduction to avoid passing on twice as many genes to the offspring. Lyon's discovery led to the discovery of X-linked diseases. When cells divide, their full genome is copied and each daughter cell inherits one copy. This process, called mitosis , is the simplest form of reproduction and is the basis for asexual reproduction. Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from

3300-425: Is a somewhat ambiguous definition of what is referred to as a gene. Trait inheritance and molecular inheritance mechanisms of genes are still primary principles of genetics in the 21st century, but modern genetics has expanded to study the function and behavior of genes. Gene structure and function, variation, and distribution are studied within the context of the cell , the organism (e.g. dominance ), and within

3410-518: Is an important branch in biology because heredity is vital to organisms' evolution . Gregor Mendel , a Moravian Augustinian friar working in the 19th century in Brno , was the first to study genetics scientifically. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms (pea plants) inherit traits by way of discrete "units of inheritance". This term, still used today,

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3520-482: Is caused by genetic or postnatal environmental factors. One famous example involved the study of the Genain quadruplets , who were identical quadruplets all diagnosed with schizophrenia . The genome of a given organism contains thousands of genes, but not all these genes need to be active at any given moment. A gene is expressed when it is being transcribed into mRNA and there exist many cellular methods of controlling

3630-425: Is controlled by the insect. Galls act as both the habitat and food source for the maker of the gall. The interior of a gall can contain edible nutritious starch and other tissues. Some galls act as "physiologic sinks", concentrating resources in the gall from the surrounding plant parts. Galls may also provide the insect with physical protection from predators. Insect galls are usually induced by chemicals injected by

3740-446: Is induction begins with insect saliva on plants. Insect saliva contains various chemicals, induces shock and osmotic changes in the host plant cell. The severity of insect feeding injures the plant varies depending on the insect. The osmotic changes that occur as a result are characterized by increased quantities of osmotically active material and induce the cell metaplasia and gall formation. Gall growth occurs gradually over time, with

3850-421: Is influenced by plant vigor and module size, with larger, fast-growing plant modules resulting in larger galls. Conversely, galls are easily induced on smaller plant modules. Galls are unique growths on plants, and how the plant's genetic instructions could produce these structures in response to external factors is still a fresh field of science. Genetic mechanisms of gall formation is a unique interplay between

3960-441: Is responsible for the development of structures within multicellular organisms, these patterns arise from the complex interactions between many cells. Within eukaryotes , there exist structural features of chromatin that influence the transcription of genes, often in the form of modifications to DNA and chromatin that are stably inherited by daughter cells. These features are called " epigenetic " because they exist "on top" of

4070-497: Is the physical basis for inheritance: DNA replication duplicates the genetic information by splitting the strands and using each strand as a template for synthesis of a new partner strand. Genes are arranged linearly along long chains of DNA base-pair sequences. In bacteria , each cell usually contains a single circular genophore , while eukaryotic organisms (such as plants and animals) have their DNA arranged in multiple linear chromosomes. These DNA strands are often extremely long;

4180-694: Is the same as that which Mendel published. In his third law, he developed the basic principles of mutation (he can be considered a forerunner of Hugo de Vries ). Festetics argued that changes observed in the generation of farm animals, plants, and humans are the result of scientific laws. Festetics empirically deduced that organisms inherit their characteristics, not acquire them. He recognized recessive traits and inherent variation by postulating that traits of past generations could reappear later, and organisms could produce progeny with different attributes. These observations represent an important prelude to Mendel's theory of particulate inheritance insofar as it features

4290-486: The Blue-eyed Mary ( Omphalodes verna ), for example, there exists a gene with alleles that determine the color of flowers: blue or magenta. Another gene, however, controls whether the flowers have color at all or are white. When a plant has two copies of this white allele, its flowers are white—regardless of whether the first gene has blue or magenta alleles. This interaction between genes is called epistasis , with

4400-413: The ancient Greek γενετικός genetikos meaning "genitive"/"generative", which in turn derives from γένεσις genesis meaning "origin". The observation that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding . The modern science of genetics, seeking to understand this process, began with

4510-418: The larvae of the insects into the plants and possibly mechanical damage. After the galls are formed, the larvae develop inside until fully grown, when they leave. To form galls, the insects must take advantage of the time when plant cell division occurs quickly: the growing season, usually spring in temperate climates, but which is extended in the tropics. The meristems , where plant cell division occurs, are

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4620-415: The neutral theory of molecular evolution through publishing the nearly neutral theory of molecular evolution . In this theory, Ohta stressed the importance of natural selection and the environment to the rate at which genetic evolution occurs. One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger . This technology allows scientists to read the nucleotide sequence of

4730-622: The woolly aphid Adelges abietis , which parasitises coniferous trees such as the Sitka spruce and the Norway spruce. Some dipteran flies such as the cecidomyiid gall midges Dasineura investita and Neolasioptera boehmeriae , and some Agromyzidae leaf-miner flies cause galls. Mites, small arachnids, cause distinctive galls in plants such as the lime tree . Nematodes are microscopic worms that live in soil. Some nematodes ( Meloidogyne species or root-knot nematodes ) cause galls on

4840-421: The DNA sequence and retain inheritance from one cell generation to the next. Because of epigenetic features, different cell types grown within the same medium can retain very different properties. Although epigenetic features are generally dynamic over the course of development, some, like the phenomenon of paramutation , have multigenerational inheritance and exist as rare exceptions to the general rule of DNA as

4950-632: The F1 offspring mate with each other, the offspring are called the "F2" (second filial) generation. One of the common diagrams used to predict the result of cross-breeding is the Punnett square . When studying human genetic diseases, geneticists often use pedigree charts to represent the inheritance of traits. These charts map the inheritance of a trait in a family tree. Organisms have thousands of genes, and in sexually reproducing organisms these genes generally assort independently of each other. This means that

5060-504: The Greek word genesis —γένεσις, "origin", predates the noun and was first used in a biological sense in 1860. Bateson both acted as a mentor and was aided significantly by the work of other scientists from Newnham College at Cambridge, specifically the work of Becky Saunders , Nora Darwin Barlow , and Muriel Wheldale Onslow . Bateson popularized the usage of the word genetics to describe

5170-448: The ability of the body to break down the amino acid phenylalanine , causing a toxic build-up of an intermediate molecule that, in turn, causes severe symptoms of progressive intellectual disability and seizures. However, if someone with the phenylketonuria mutation follows a strict diet that avoids this amino acid, they remain normal and healthy. A common method for determining how genes and environment ("nature and nurture") contribute to

5280-444: The adaptive function of repair of DNA damages. The first cytological demonstration of crossing over was performed by Harriet Creighton and Barbara McClintock in 1931. Their research and experiments on corn provided cytological evidence for the genetic theory that linked genes on paired chromosomes do in fact exchange places from one homolog to the other. The probability of chromosomal crossover occurring between two given points on

5390-425: The adult exits either by chewing its way out or utilizing an opening created by the larval stage. Conversely, insects with sucking mouthparts rely on partially open galls or those that naturally open to facilitate emergence. An example of the latter type is the aphid, which forms marble-sized galls on the leaf stems of cottonwood trees. While these galls have thin walls, they harbor entire colonies of aphids within. When

5500-440: The basis for inheritance. During the process of DNA replication, errors occasionally occur in the polymerization of the second strand. These errors, called mutations, can affect the phenotype of an organism, especially if they occur within the protein coding sequence of a gene. Error rates are usually very low—1 error in every 10–100 million bases—due to the "proofreading" ability of DNA polymerases . Processes that increase

5610-404: The cat plays the role of the environment. The cat's genes code for dark hair, thus the hair-producing cells in the cat make cellular proteins resulting in dark hair. But these dark hair-producing proteins are sensitive to temperature (i.e. have a mutation causing temperature-sensitivity) and denature in higher-temperature environments, failing to produce dark-hair pigment in areas where the cat has

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5720-429: The cell, these genes for tryptophan synthesis are no longer needed. The presence of tryptophan directly affects the activity of the genes—tryptophan molecules bind to the tryptophan repressor (a transcription factor), changing the repressor's structure such that the repressor binds to the genes. The tryptophan repressor blocks the transcription and expression of the genes, thereby creating negative feedback regulation of

5830-421: The chromosome is related to the distance between the points. For an arbitrarily long distance, the probability of crossover is high enough that the inheritance of the genes is effectively uncorrelated. For genes that are closer together, however, the lower probability of crossover means that the genes demonstrate genetic linkage; alleles for the two genes tend to be inherited together. The amounts of linkage between

5940-422: The combined DNA sequences of all chromosomes) is called the genome . DNA is most often found in the nucleus of cells, but Ruth Sager helped in the discovery of nonchromosomal genes found outside of the nucleus. In plants, these are often found in the chloroplasts and in other organisms, in the mitochondria. These nonchromosomal genes can still be passed on by either partner in sexual reproduction and they control

6050-486: The context of a population. Genetics has given rise to a number of subfields, including molecular genetics , epigenetics , and population genetics . Organisms studied within the broad field span the domains of life ( archaea , bacteria , and eukarya ). Genetic processes work in combination with an organism's environment and experiences to influence development and behavior , often referred to as nature versus nurture . The intracellular or extracellular environment of

6160-483: The developing gall wasp larva. The defense-related genes are found to be suppressed in inner gall tissues as a strategy to accommodate the feeding activity of the parasite. Plant galls are caused by a wide range of organisms, including animals such as insects, mites, and nematodes; fungi; bacteria; viruses; and other plants. Insect galls are the highly distinctive plant structures formed by some herbivorous insects as their own microhabitats. They are plant tissue which

6270-517: The efficacy of resistance genes deployed in agriculture. The evolutionary arms race between plants and parasites, underscored by the expansion of gene families involved in biotic interactions, shapes their genomic landscape, influencing their adaptive strategies and diversification. Crown galls formed under the influence of the bacterium Agrobacterium tumefaciens exhibit several distinctive characteristics when compared to other types of galls. This bacterium transfers genetic material known as T-DNA into

6380-581: The establishment of metaplasied cells and localized metabolic changes to repair the wound and neutralize stress. Osmotic stress leads to the development of metaplasied cells, characterized by increased quantities of osmotically active material. The rejection response by the plant triggers the synthesis of defense compounds and enzymes . There are two primary categories of galls: closed and open. Insects such as wasps, moths, and flies, possessing chewing mouthparts during their adult or larval stages, typically inhabit completely enclosed galls. Upon reaching maturity,

6490-417: The expression of genes such that proteins are produced only when needed by the cell. Transcription factors are regulatory proteins that bind to DNA, either promoting or inhibiting the transcription of a gene. Within the genome of Escherichia coli bacteria, for example, there exists a series of genes necessary for the synthesis of the amino acid tryptophan . However, when tryptophan is already available to

6600-411: The gall while defense gradient to the opposite direction. Gall morphogenesis involves the regulation of the organ on which the gall occurs while maintaining differentiation freedom. Gall development begins from a single or group of metaplasied cells and progresses through promoter-mediated cell expansion, cell multiplication, programmed differentiation, and control of symmetry. Plant response involves

6710-502: The glasshouse in the later stages of infection. The causal agent was transmitted by the hemipteran bug Nephotettix nigropictus after an incubation of two weeks. Polyhedral particles of 65 nm diameter in the cytoplasm of phloem cells were always associated with the disease. No serologic relationship was found between this virus and that of rice dwarf. The hemiparasitic plant mistletoe forms woody structures sometimes called galls on its hosts. More complex interactions are possible;

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6820-469: The information an organism uses to function, the environment plays an important role in determining the ultimate phenotypes an organism displays. The phrase " nature and nurture " refers to this complementary relationship. The phenotype of an organism depends on the interaction of genes and the environment. An interesting example is the coat coloration of the Siamese cat . In this case, the body temperature of

6930-406: The inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. This phenomenon, known as " Mendel's second law " or the "law of independent assortment," means that the alleles of different genes get shuffled between parents to form offspring with many different combinations. Different genes often interact to influence the same trait. In

7040-802: The initial defense layer of plant cells, activated upon detection of "danger signals." These signals, termed damage-associated-molecular-patterns (DAMPs) if originating from the plant or microbe/pathogen-associated-molecular-patterns (MAMPs, PAMPs, or HAMPs) if from the parasite, engage pattern-recognition receptors (PRRs) triggering signaling cascades. PRRs, classified as receptor-like kinases (RLKs), mediate intercellular communication by bridging external stimuli with intracellular defense mechanisms. Antagonists, employing effector-triggered susceptibility (ETS) manipulate host-cell functions through effector molecules encoded by effector genes, aiming primarily at suppressing plant defenses. Notably, some effectors exploit plant traits, known as "plant susceptibility traits," diverting

7150-427: The largest human chromosome, for example, is about 247 million base pairs in length. The DNA of a chromosome is associated with structural proteins that organize, compact, and control access to the DNA, forming a material called chromatin ; in eukaryotes, chromatin is usually composed of nucleosomes , segments of DNA wound around cores of histone proteins. The full set of hereditary material in an organism (usually

7260-490: The length, breadth, and height of the galls increasing proportionally. The growth rate is maximal during the insect's early developmental stages and slows as it approaches adulthood. Hormones like auxins play a crucial role in gall growth. The presence of stress and insect secretions stimulates the synthesis of growth-promoting substances, possibly involving a combination of different growth promoters like auxins and kinins. Gall growth involves both cell enlargement and division, but

7370-529: The manufacturing of permanent inks (such as iron gall ink ) and astringent ointments, in dyeing , and in leather tanning . The Talmud records using gallnuts as part of the tanning process as well as a dye-base for ink. Medieval Arabic literature records many uses for the gall, called ˁafṣ in Arabic. The Aleppo gall , found on oak trees in northern Syria , was among the most important exports from Syria during this period, with one merchant recording

7480-571: The nature of inheritance in plants. In his paper " Versuche über Pflanzenhybriden " (" Experiments on Plant Hybridization "), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brno , Mendel traced the inheritance patterns of certain traits in pea plants and described them mathematically. Although this pattern of inheritance could only be observed for a few traits, Mendel's work suggested that heredity

7590-446: The observation of 3-D cell morphology with both high spatial and temporal resolution. The dynamic processes of this cell morphology which are controlled by a complex system play an important role in varied important biological processes, such as immune and invasive responses. Genetics This is an accepted version of this page Genetics is the study of genes , genetic variation , and heredity in organisms . It

7700-500: The offspring of a mating pair. Genes on the same chromosome would theoretically never recombine. However, they do, via the cellular process of chromosomal crossover . During crossover, chromosomes exchange stretches of DNA, effectively shuffling the gene alleles between the chromosomes. This process of chromosomal crossover generally occurs during meiosis , a series of cell divisions that creates haploid cells. Meiotic recombination , particularly in microbial eukaryotes , appears to serve

7810-435: The original sequence. A particularly important source of DNA damages appears to be reactive oxygen species produced by cellular aerobic respiration , and these can lead to mutations. In organisms that use chromosomal crossover to exchange DNA and recombine genes, errors in alignment during meiosis can also cause mutations. Errors in crossover are especially likely when similar sequences cause partner chromosomes to adopt

7920-422: The outer gall transcriptome resembles that of twigs, leaf buds, and reproductive structures, the inner gall transcriptome is distinct from normal oak tissues, underscoring the complexity of gall formation. Furthermore, there is an upregulation of genes related to sugar and amino acid metabolism in both outer and inner gall tissues, suggesting a role in transporting plant metabolites to support the nutritional needs of

8030-465: The outward appearance (shape, structure, color, pattern, size), i.e. external morphology (or eidonomy ), as well as the form and structure of internal parts like bones and organs , i.e. internal morphology (or anatomy ). This is in contrast to physiology , which deals primarily with function. Morphology is a branch of life science dealing with the study of the gross structure of an organism or taxon and its component parts. The etymology of

8140-405: The parasite and the host plant in shaping the developmental trajectory of the gall organ. The 'zigzag' model introduced by Jones & Dangl (2006) demonstrates the molecular interactions underlying gall induction. This model, refined over time and subject to ongoing enhancements, illustrates the intricate dynamics between antagonistic molecular players. Pattern-triggered immunity (PTI), constitutes

8250-488: The parasitic plant Cassytha filiformis sometimes preferentially feeds on galls induced by the cynipid wasp Belonocnema treatae . Insects induce the formation of galls on plants from which they receive various services, such as a source of nutrition and a place to lay eggs, develop, and be provided protection from the environment and enemies. The gall producers are specific to specific plants, thus inducing galls with unique appearances (balls, knobs, lumps, warts, etc.) and

8360-470: The phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once. When a pair of organisms reproduce sexually , their offspring randomly inherit one of the two alleles from each parent. These observations of discrete inheritance and

8470-528: The physical actions and chemical stimuli of different insects. Around 90% of galls occur on the leaves of dicotyledons . Galls can develop on various parts of the host plant, such as roots, leaf bases, branches, or leaflets. Internally, galls also exhibit diverse structures. Some are simple, comprising only outgrown and curved leaf tissues, while others feature complex, hierarchical arrangements with multiple chambers containing different types of tissues, including collenchyma , parenchyma , physalides-parenchyma, and

8580-596: The plant and causing growth suppression elsewhere. The bacteria possess virulence genes that control their ability to colonize plants and produce cytokinins, which influence plant growth. While parasitic gall-inducers are typically harmful to plants, researchers are exploring ways to harness their growth-promoting abilities for agricultural benefit. Some derivatives of R. fascians are being investigated for their potential to promote balanced plant growth, and scientists are also studying plant interactions with these bacteria to discover traits that could enhance crop yields. Most of

8690-509: The plant cells, where it becomes integrated into the chromosomes . The T-DNA contains genes that encode for production of auxin, cytokinin and opines. As a result, the infected plant cells undergo rapid multiplication, essentially transforming into "bacterial factories" that produce more bacterial bodies. Certain bacteria, like Rhodococcus fascians , induce the formation of leafy galls on plants, affecting their growth. These galls act as permanent sinks, diverting nutrients away from other parts of

8800-601: The plant's resources in favor of the parasite. Effectoromics, involving high-throughput expression screens, aids in identifying effector candidates crucial for colonization. Conversely, Effector-Triggered Immunity (ETI) responsible for plant's counterattack, leveraging effectors as "danger signals" to render the parasite avirulent. During ETI, nucleotide-binding domain leucine-rich repeat (NLR)-containing receptors detect perturbations induced by effectors, leading to downstream signaling events that promote defense responses. However, parasites can counteract ETI by modifying ETS, undermining

8910-543: The process of protein production . It was discovered that the cell uses DNA as a template to create matching messenger RNA , molecules with nucleotides very similar to DNA. The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide sequences and amino acid sequences is known as the genetic code . With the newfound molecular understanding of inheritance came an explosion of research. A notable theory arose from Tomoko Ohta in 1973 with her amendment to

9020-435: The product rule, the sum rule, and more. Geneticists use diagrams and symbols to describe inheritance. A gene is represented by one or a few letters. Often a "+" symbol is used to mark the usual, non-mutant allele for a gene. In fertilization and breeding experiments (and especially when discussing Mendel's laws) the parents are referred to as the "P" generation and the offspring as the "F1" (first filial) generation. When

9130-519: The properties of a protein by destabilizing the structure or changing the surface of the protein in a way that changes its interaction with other proteins and molecules. For example, sickle-cell anemia is a human genetic disease that results from a single base difference within the coding region for the β-globin section of hemoglobin, causing a single amino acid change that changes hemoglobin's physical properties. Sickle-cell versions of hemoglobin stick to themselves, stacking to form fibers that distort

9240-426: The protein itself). Protein structure is dynamic; the protein hemoglobin bends into slightly different forms as it facilitates the capture, transport, and release of oxygen molecules within mammalian blood. A single nucleotide difference within DNA can cause a change in the amino acid sequence of a protein. Because protein structures are the result of their amino acid sequences, some changes can dramatically change

9350-406: The rate of changes in DNA are called mutagenic : mutagenic chemicals promote errors in DNA replication, often by interfering with the structure of base-pairing, while UV radiation induces mutations by causing damage to the DNA structure. Chemical damage to DNA occurs naturally as well and cells use DNA repair mechanisms to repair mismatches and breaks. The repair does not, however, always restore

9460-522: The roots of susceptible plants. The galls are often small. Many rust fungi induce gall formation, including western gall rust , which infects a variety of pine trees and cedar-apple rust . Galls are often seen in Millettia pinnata leaves and fruits. Leaf galls appear like tiny clubs; however, flower galls are globose. Exobasidium often induces spectacular galls on its hosts. The fungus Ustilago esculenta associated with Zizania latifolia ,

9570-408: The same allele of a given gene are called homozygous at that gene locus , while organisms with two different alleles of a given gene are called heterozygous . The set of alleles for a given organism is called its genotype , while the observable traits of the organism are called its phenotype . When organisms are heterozygous at a gene, often one allele is called dominant as its qualities dominate

9680-401: The second gene epistatic to the first. Many traits are not discrete features (e.g. purple or white flowers) but are instead continuous features (e.g. human height and skin color ). These complex traits are products of many genes. The influence of these genes is mediated, to varying degrees, by the environment an organism has experienced. The degree to which an organism's genes contribute to

9790-509: The segregation of alleles are collectively known as Mendel's first law or the Law of Segregation. However, the probability of getting one gene over the other can change due to dominant, recessive, homozygous, or heterozygous genes. For example, Mendel found that if you cross heterozygous organisms your odds of getting the dominant trait is 3:1. Real geneticist study and calculate probabilities by using theoretical probabilities, empirical probabilities,

9900-653: The shape of red blood cells carrying the protein. These sickle-shaped cells no longer flow smoothly through blood vessels , having a tendency to clog or degrade, causing the medical problems associated with this disease. Some DNA sequences are transcribed into RNA but are not translated into protein products—such RNA molecules are called non-coding RNA . In some cases, these products fold into structures which are involved in critical cell functions (e.g. ribosomal RNA and transfer RNA ). RNA can also have regulatory effects through hybridization interactions with other RNA molecules (such as microRNA ). Although genes contain all

10010-446: The similar molecule RNA instead of DNA as their genetic material. DNA normally exists as a double-stranded molecule, coiled into the shape of a double helix . Each nucleotide in DNA preferentially pairs with its partner nucleotide on the opposite strand: A pairs with T, and C pairs with G. Thus, in its two-stranded form, each strand effectively contains all necessary information, redundant with its partner strand. This structure of DNA

10120-500: The single celled alga Acetabularia . The Hershey–Chase experiment in 1952 confirmed that DNA (rather than protein) is the genetic material of the viruses that infect bacteria, providing further evidence that DNA is the molecule responsible for inheritance. James Watson and Francis Crick determined the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin and Maurice Wilkins that indicated DNA has

10230-534: The specific factors triggering cell enlargement remain unclear. The earliest impact from the insect leads to metaplasia in the affected cells, where they undergo changes in structure and function. When the chemical shock is of high intensity, metaplasia does not occur. Instead, the plant cells local to the shock die, thereby rejecting the insect and defending the plant tissue. Enzymes like invertases are involved in gall growth, with greater activity correlating with stronger gall development. Gall-inducing insect performance

10340-441: The strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand. This property is what gives DNA its semi-conservative nature where one strand of new DNA is from an original parent strand. Although the structure of DNA showed how inheritance works, it was still not known how DNA influences the behavior of cells. In the following years, scientists tried to understand how DNA controls

10450-580: The study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London in 1906. After the rediscovery of Mendel's work, scientists tried to determine which molecules in the cell were responsible for inheritance. In 1900, Nettie Stevens began studying the mealworm. Over the next 11 years, she discovered that females only had the X chromosome and males had both X and Y chromosomes. She

10560-467: The time is right, a slit appears on one side of the gall, allowing the aphids to escape as the slit's lips unfold. Insects induce the formation of galls on plants from which they receive various services, such as a source of nutrition and a place to lay eggs, develop, and be provided protection from the environment and enemies. The gall producers are specific to specific plants, thus inducing galls with unique appearances (balls, knobs, lumps, warts, etc.) and

10670-404: The tissue-specific gene expression. There are substantial differences in  gene expression between inner and outer gall tissues compared to adjacent leaf tissues. Notably, approximately 28% of oak genes display differential expression in the gall compared to leaves, indicating significant transcriptional changes associated with gall development. According to the transcriptome analysis , while

10780-407: The transcriptomic studies on plant galls used entire gall samples resulting both gall and non-gall cells leading to thousands of gene expressions during gall development. Recent studies on gall induced by gall wasps (Hymenoptera: Cynipidae) Dryocosmus quercuspalustris on northern red oak ( Quercus rubra L. ) leaves demonstrate the complexity of genetic mechanisms underlying galls by quantifying

10890-611: The tribe Cynipini , their hosts mostly being oak trees and other members of the Fagaceae (the beech tree family). These are often restricted taxonomically to a single host species or a group of related species. Some wasps from other groups, such as the Diplolepididae and the Chalcidoidea , also cause plant galls. Among the hemipteran bugs that cause galls are the psyllid bug Pachypsylla celtidisumbilicus , and

11000-536: The tryptophan synthesis process. Differences in gene expression are especially clear within multicellular organisms , where cells all contain the same genome but have very different structures and behaviors due to the expression of different sets of genes. All the cells in a multicellular organism derive from a single cell, differentiating into variant cell types in response to external and intercellular signals and gradually establishing different patterns of gene expression to create different behaviors. As no single gene

11110-482: The twenty possible amino acids in a protein or an instruction to end the amino acid sequence ; this correspondence is called the genetic code . The flow of information is unidirectional: information is transferred from nucleotide sequences into the amino acid sequence of proteins, but it never transfers from protein back into the sequence of DNA—a phenomenon Francis Crick called the central dogma of molecular biology . The specific sequence of amino acids results in

11220-545: The two is responsible for inheritance. In 1928 , Frederick Griffith discovered the phenomenon of transformation : dead bacteria could transfer genetic material to "transform" other still-living bacteria. Sixteen years later, in 1944, the Avery–MacLeod–McCarty experiment identified DNA as the molecule responsible for transformation. The role of the nucleus as the repository of genetic information in eukaryotes had been established by Hämmerling in 1943 in his work on

11330-576: The use of allometric engineering in which one or both species are manipulated to phenocopy the other species. A step relevant to the evaluation of morphology between traits/features within species, includes an assessment of the terms: homology and homoplasy . Homology between features indicates that those features have been derived from a common ancestor. Alternatively, homoplasy between features describes those that can resemble each other, but derive independently via parallel or convergent evolution . The invention and development of microscopy enabled

11440-685: The usual sites of galls, though insect galls can be found on other parts of the plant, such as the leaves, stalks , branches , buds , roots , and even flowers and fruits . Gall-inducing insects are usually species-specific and sometimes tissue-specific on the plants they gall. Gall-inducing insects include gall wasps , gall midges , gall flies , leaf-miner flies , aphids , scale insects , psyllids , thrips , gall moths, and weevils . Many gall insects remain to be described. Estimates range up to more than 210,000 species, not counting parasitoids of gall-forming insects. More than 1400 species of cynipid wasps cause galls. Some 1000 of these are in

11550-774: The word "morphology" is from the Ancient Greek μορφή ( morphḗ ), meaning "form", and λόγος ( lógos ), meaning "word, study, research". While the concept of form in biology, opposed to function , dates back to Aristotle (see Aristotle's biology ), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist and physiologist Karl Friedrich Burdach (1800). Among other important theorists of morphology are Lorenz Oken , Georges Cuvier , Étienne Geoffroy Saint-Hilaire , Richard Owen , Carl Gegenbaur and Ernst Haeckel . In 1830, Cuvier and Saint-Hilaire engaged in

11660-538: The work of the Augustinian friar Gregor Mendel in the mid-19th century. Prior to Mendel, Imre Festetics , a Hungarian noble, who lived in Kőszeg before Mendel, was the first who used the word "genetic" in hereditarian context, and is considered the first geneticist. He described several rules of biological inheritance in his work The genetic laws of nature (Die genetischen Gesetze der Natur, 1819). His second law

11770-518: Was able to conclude that sex is a chromosomal factor and is determined by the male. In 1911, Thomas Hunt Morgan argued that genes are on chromosomes , based on observations of a sex-linked white eye mutation in fruit flies . In 1913, his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome. Although genes were known to exist on chromosomes, chromosomes are composed of both protein and DNA, and scientists did not know which of

11880-591: Was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants, showing for example that flowers on a single plant were either purple or white—but never an intermediate between the two colors. The discrete versions of the same gene controlling the inherited appearance (phenotypes) are called alleles . In the case of the pea, which is a diploid species, each individual plant has two copies of each gene, one copy inherited from each parent. Many species, including humans, have this pattern of inheritance. Diploid organisms with two copies of

11990-421: Was particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios. The importance of Mendel's work did not gain wide understanding until 1900, after his death, when Hugo de Vries and other scientists rediscovered his research. William Bateson , a proponent of Mendel's work, coined the word genetics in 1905. The adjective genetic , derived from

12100-529: Was the inheritance of acquired characteristics : the belief that individuals inherit traits strengthened by their parents. This theory (commonly associated with Jean-Baptiste Lamarck ) is now known to be wrong—the experiences of individuals do not affect the genes they pass to their children. Other theories included Darwin's pangenesis (which had both acquired and inherited aspects) and Francis Galton 's reformulation of pangenesis as both particulate and inherited. Modern genetics started with Mendel's studies of

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