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Section: Reciprocal silencing between tissues. Reciprocal silencing on the tissue level refers to the same pattern of silencing and expression of homeologous loci. However, in this case, the differences in silencing and expression occur between two types of tissue within the same individual, rather than in individuals ... | Wikipedia - Reciprocal silencing - Reciprocal silencing between tissues | 219 | 1,098 | null |
Section: For Y chromosome. In genetic genealogy, the term is used particularly concerning similar seeming events in Y chromosome DNA. This type of mutation happens within one chromosome, and does not involve a reciprocal transfer. Rather, one homologous segment "writes over" the other. The mechanism is presumed to be d... | Wikipedia - RecLOH - For Y chromosome | 335 | 1,415 | null |
PCR typing technologies have been developed (e.g. DYS464X) that are able to verify that there are most frequently really two alleles of each, so we can be sure that there is no gene deletion. Family genealogies have proven many times, that parallel changes on all markers located on the same palindrome are frequently ob... | Wikipedia - RecLOH - For Y chromosome | 153 | 590 | null |
Article: Recognition sequence. A recognition sequence is a DNA sequence to which a structural motif of a DNA-binding domain exhibits binding specificity. Recognition sequences are palindromes. The transcription factor Sp1 for example, binds the sequences 5'-(G/T)GGGCGG(G/A)(G/A)(C/T)-3', where (G/T) indicates that the ... | Wikipedia - Recognition sequence - Summary | 349 | 1,453 | null |
Section: Genotyping in transfusion medicine. Unlike traditional serological testing, which relies on the presence of antibodies to detect antigens, genotyping analyzes DNA to determine an individual's blood group profile with high accuracy. This approach is particularly valuable in complex transfusion cases, such as in... | Wikipedia - Red cell genotyping - Genotyping in transfusion medicine | 200 | 964 | null |
Section: Blood group genotyping versus Red cell genotyping. Blood group genotyping refers to the analysis of blood group antigens that are presented on the red cell membrane, including those attached to proteins, the carbohydrate components of glycoproteins and glycolipids, or anchored via Glycosylphosphatidylinositol ... | Wikipedia - Red cell genotyping - Blood group genotyping versus Red cell genotyping | 162 | 671 | null |
Article: Reproductive isolation. The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring are sterile. These barriers maintain the ... | Wikipedia - Reproductive isolation - Summary | 161 | 881 | null |
Section: Pre-zygotic isolation > Temporal or habitat isolation. Any of the factors that prevent potentially fertile individuals from meeting will reproductively isolate the members of distinct species. The types of barriers that can cause this isolation include: different habitats, physical barriers, and a difference i... | Wikipedia - Reproductive isolation - Pre-zygotic isolation > Temporal or habitat isolation | 317 | 1,644 | null |
Section: Pre-zygotic isolation > Behavioral isolation. The different mating rituals of animal species creates extremely powerful reproductive barriers, termed sexual or behavior isolation, that isolate apparently similar species in the majority of the groups of the animal kingdom. In dioecious species, males and female... | Wikipedia - Reproductive isolation - Pre-zygotic isolation > Behavioral isolation | 346 | 1,808 | null |
Drosophila ananassae and D. pallidosa are twin species from Melanesia. In the wild they rarely produce hybrids, although in the laboratory it is possible to produce fertile offspring. Studies of their sexual behavior show that the males court the females of both species but the females show a marked preference for mati... | Wikipedia - Reproductive isolation - Pre-zygotic isolation > Behavioral isolation | 294 | 1,417 | null |
There are two twin species in Europe that occasionally cross. The females of both species produce pheromones that contain a volatile compound which has two isomers, E and Z; 99% of the compound produced by the females of one species is in the E isomer form, while the females of the other produce 99% isomer Z. The produ... | Wikipedia - Reproductive isolation - Pre-zygotic isolation > Behavioral isolation | 333 | 1,618 | null |
Section: Pre-zygotic isolation > Mechanical isolation. Mating pairs may not be able to couple successfully if their genitals are not compatible. The relationship between the reproductive isolation of species and the form of their genital organs was signaled for the first time in 1844 by the French entomologist Léon Duf... | Wikipedia - Reproductive isolation - Pre-zygotic isolation > Mechanical isolation | 265 | 1,397 | null |
Section: Pre-zygotic isolation > Gametic isolation. The synchronous spawning of many species of coral in marine reefs means that inter-species hybridization can take place as the gametes of hundreds of individuals of tens of species are liberated into the same water at the same time. Approximately a third of all the po... | Wikipedia - Reproductive isolation - Pre-zygotic isolation > Gametic isolation | 343 | 1,605 | null |
However, the growth of the pollen tubes may be detained at some point between the stigma and the ovules, in such a way that fertilization does not take place. This mechanism of reproductive isolation is common in the angiosperms and is called cross-incompatibility or incongruence. A relationship exists between self-inc... | Wikipedia - Reproductive isolation - Pre-zygotic isolation > Gametic isolation | 170 | 760 | null |
Section: Post-zygotic isolation > Zygote mortality and non-viability of hybrids. A type of incompatibility that is found as often in plants as in animals occurs when the egg or ovule is fertilized but the zygote does not develop, or it develops and the resulting individual has a reduced viability. This is the case for ... | Wikipedia - Reproductive isolation - Post-zygotic isolation > Zygote mortality and non-viability of hybrids | 313 | 1,470 | null |
Section: Post-zygotic isolation > Hybrid sterility. A hybrid may have normal viability but is typically deficient in terms of reproduction or is sterile. This is demonstrated by the mule and in many other well known hybrids. In all of these cases sterility is due to the interaction between the genes of the two species ... | Wikipedia - Reproductive isolation - Post-zygotic isolation > Hybrid sterility | 322 | 1,458 | null |
Interspecific sterility of hybrids in plants has multiple possible causes. These may be genetic, related to the genomes, or the interaction between nuclear and cytoplasmic factors, as will be discussed in the corresponding section. Nevertheless, in plants, hybridization is a stimulus for the creation of new species – t... | Wikipedia - Reproductive isolation - Post-zygotic isolation > Hybrid sterility | 203 | 899 | null |
Section: Multiple mechanisms. In general, the barriers that separate species do not consist of just one mechanism. The twin species of Drosophila, D. pseudoobscura and D. persimilis, are isolated from each other by habitat (persimilis generally lives in colder regions at higher altitudes), by the timing of the mating s... | Wikipedia - Reproductive isolation - Multiple mechanisms | 259 | 1,278 | null |
Section: Hybrid sex: Haldane's rule. Haldane's rule states that when one of the two sexes is absent in interspecific hybrids between two specific species, then the sex that is not produced, is rare or is sterile is the heterozygous (or heterogametic) sex. In mammals, at least, there is growing evidence to suggest that ... | Wikipedia - Reproductive isolation - Hybrid sex: Haldane's rule | 284 | 1,246 | null |
Section: Genetics > Pre-copulatory mechanisms in animals. The genetics of ethological isolation barriers will be discussed first. Pre-copulatory isolation occurs when the genes necessary for the sexual reproduction of one species differ from the equivalent genes of another species, such that if a male of species A and ... | Wikipedia - Reproductive isolation - Genetics > Pre-copulatory mechanisms in animals | 328 | 1,634 | null |
Section: Genetics > Post-copulation or fertilization mechanisms in animals. Reproductive isolation between species appears, in certain cases, a long time after fertilization and the formation of the zygote, as happens – for example – in the twin species Drosophila pavani and D. gaucha. The hybrids between both species ... | Wikipedia - Reproductive isolation - Genetics > Post-copulation or fertilization mechanisms in animals | 347 | 1,686 | null |
From this perspective, only a few genes would be required in order to bring about post copulatory isolation, as opposed to the situation described previously for pre-copulatory isolation. In many species where pre-copulatory reproductive isolation does not exist, hybrids are produced but they are of only one sex. This ... | Wikipedia - Reproductive isolation - Genetics > Post-copulation or fertilization mechanisms in animals | 348 | 1,686 | null |
As important as identifying an isolation gene is knowing its function. The Hmr gene, linked to the X chromosome and implicated in the viability of male hybrids between D. melanogaster and D. simulans, is a gene from the proto-oncogene family myb, that codes for a transcriptional regulator. Two variants of this gene fun... | Wikipedia - Reproductive isolation - Genetics > Post-copulation or fertilization mechanisms in animals | 322 | 1,589 | null |
An important unanswered question is whether the genes detected correspond to old genes that initiated the speciation favoring hybrid non-viability, or are modern genes that have appeared post-speciation by mutation, that are not shared by the different populations and that suppress the effect of the primitive non-viabi... | Wikipedia - Reproductive isolation - Genetics > Post-copulation or fertilization mechanisms in animals | 342 | 1,665 | null |
It regulates the production of one of the approximately 30 proteins required to form a nuclear pore. In each of the simulans groups of Drosophila the protein from this gene interacts with the protein from another, as yet undiscovered, gene on the X chromosome in order to form a functioning pore. However, in a hybrid th... | Wikipedia - Reproductive isolation - Genetics > Post-copulation or fertilization mechanisms in animals | 325 | 1,554 | null |
There is no sexual isolation between them and the F1 hybrid is fertile. However, the F2 hybrids are relatively infertile and leave few descendants which have a skewed ratio of the sexes. The reason is that the X chromosome of albomicans is translocated and linked to an autosome which causes abnormal meiosis in hybrids.... | Wikipedia - Reproductive isolation - Genetics > Post-copulation or fertilization mechanisms in animals | 170 | 844 | null |
Section: Genetics > In plants. A large variety of mechanisms have been demonstrated to reinforce reproductive isolation between closely related plant species that either historically lived or currently live in sympatry. This phenomenon is driven by strong selection against hybrids, typically resulting from instances in... | Wikipedia - Reproductive isolation - Genetics > In plants | 344 | 1,796 | null |
Section: Genetics > Examples of pre-fertilization mechanisms. A well-documented example of a pre-fertilization isolating mechanism comes from study of Louisiana iris species. These iris species were fertilized with interspecific and conspecific pollen loads and it was demonstrated by measure of hybrid progeny success t... | Wikipedia - Reproductive isolation - Genetics > Examples of pre-fertilization mechanisms | 221 | 1,082 | null |
Section: Genetics > Incompatibility caused by microorganisms. In addition to the genetic causes of reproductive isolation between species there is another factor that can cause post zygotic isolation: the presence of microorganisms in the cytoplasm of certain species. The presence of these organisms in a species and th... | Wikipedia - Reproductive isolation - Genetics > Incompatibility caused by microorganisms | 331 | 1,513 | null |
Section: Selection. In 1950 K. F. Koopman reported results from experiments designed to examine the hypothesis that selection can increase reproductive isolation between populations. He used D. pseudoobscura and D. persimilis in these experiments. When the flies of these species are kept at 16 °C approximately a third ... | Wikipedia - Reproductive isolation - Selection | 305 | 1,697 | null |
These discoveries allowed certain assumptions to be made regarding the origin of reproductive isolation mechanisms in nature. Namely, if selection reinforces the degree of reproductive isolation that exists between two species due to the poor adaptive value of the hybrids, it is expected that the populations of two spe... | Wikipedia - Reproductive isolation - Selection | 333 | 1,758 | null |
Article: Restriction map. A restriction map is a map of known restriction sites within a sequence of DNA. Restriction mapping requires the use of restriction enzymes. In molecular biology, restriction maps are used as a reference to engineer plasmids or other relatively short pieces of DNA, and sometimes for longer gen... | Wikipedia - Restriction map - Summary | 229 | 1,218 | null |
Section: Method. The experimental procedure first requires a sample of purified plasmid DNA for each digest to be run. Digestion is then performed with each enzyme(s) chosen. The resulting samples are subsequently run on an electrophoresis gel, typically on agarose gel. The first step following the completion of electr... | Wikipedia - Restriction map - Method | 254 | 1,204 | null |
Section: Method > Rapid Denaturation and Renaturation of a crude DNA preparation by alkaline lysis of the cells and subsequent neutralization. In this technique the cells are lysed in alkaline conditions. The DNA in the mixture is denatured (strands separated) by disrupting the hydrogen bonds between the two strands. T... | Wikipedia - Restriction map - Method > Rapid Denaturation and Renaturation of a crude DNA preparation by alkaline lysis of the cells and subsequent neutralization | 197 | 917 | null |
Article: Ribosomal frameshift. Ribosomal frameshifting, also known as translational frameshifting or translational recoding, is a biological phenomenon that occurs during translation that results in the production of multiple, unique proteins from a single mRNA. The process can be programmed by the nucleotide sequence ... | Wikipedia - Ribosomal frameshift - Summary | 183 | 828 | null |
Section: Process overview > DNA example. In this example, the following sequence is a region of the human mitochondrial genome with the two overlapping genes MT-ATP8 and MT-ATP6. When read from the beginning, these codons make sense to a ribosome and can be translated into amino acids (AA) under the vertebrate mitochon... | Wikipedia - Ribosomal frameshift - Process overview > DNA example | 230 | 854 | null |
Section: Function in viruses and eukaryotes. In viruses this phenomenon may be programmed to occur at particular sites and allows the virus to encode multiple types of proteins from the same mRNA. Notable examples include HIV-1 (human immunodeficiency virus), RSV (Rous sarcoma virus) and the influenza virus (flu), whic... | Wikipedia - Ribosomal frameshift - Function in viruses and eukaryotes | 158 | 730 | null |
Section: Types of frameshifting > Programmed −1 ribosomal frameshifting. In −1 frameshifting, the ribosome slips back one nucleotide and continues translation in the −1 frame. There are typically three elements that comprise a −1 frameshift signal: a slippery sequence, a spacer region, and an RNA secondary structure. T... | Wikipedia - Ribosomal frameshift - Types of frameshifting > Programmed −1 ribosomal frameshifting | 311 | 1,275 | null |
Section: Types of frameshifting > +1 ribosomal frameshifting. The slippery sequence for a +1 frameshift signal does not have the same motif, and instead appears to function by pausing the ribosome at a sequence encoding a rare amino acid. Ribosomes do not translate proteins at a steady rate, regardless of the sequence.... | Wikipedia - Ribosomal frameshift - Types of frameshifting > +1 ribosomal frameshifting | 188 | 846 | null |
Section: Controlling mechanisms > Frameshift signal elements > Slippery sequence. Slippery sequences can potentially make the reading ribosome "slip" and skip a number of nucleotides (usually only 1) and read a completely different frame thereafter. In programmed −1 ribosomal frameshifting, the slippery sequence fits a... | Wikipedia - Ribosomal frameshift - Controlling mechanisms > Frameshift signal elements > Slippery sequence | 193 | 832 | null |
Section: Controlling mechanisms > Frameshift signal elements > RNA secondary structure. Efficient ribosomal frameshifting generally requires the presence of an RNA secondary structure to enhance the effects of the slippery sequence. The RNA structure (which can be a stem-loop or pseudoknot) is thought to pause the ribo... | Wikipedia - Ribosomal frameshift - Controlling mechanisms > Frameshift signal elements > RNA secondary structure | 347 | 1,749 | null |
Section: Classification > Mutational robustness. Mutational robustness (also called mutation tolerance) describes the extent to which an organism's phenotype remains constant in spite of mutation. Robustness can be empirically measured for several genomes and individual genes by inducing mutations and measuring what pr... | Wikipedia - Robustness (evolution) - Classification > Mutational robustness | 204 | 991 | null |
Section: Classification > Environmental robustness. In varying environments, perfect adaptation to one condition may come at the expense of adaptation to another. Consequently, the total selection pressure on an organism is the average selection across all environments weighted by the percentage time spent in that envi... | Wikipedia - Robustness (evolution) - Classification > Environmental robustness | 155 | 904 | null |
Section: Genetic, molecular and cellular causes > Protein mutational robustness. Protein mutation tolerance is the product of two main features: the structure of the genetic code and protein structural robustness. Proteins are resistant to mutations because many sequences can fold into highly similar structural folds. ... | Wikipedia - Robustness (evolution) - Genetic, molecular and cellular causes > Protein mutational robustness | 235 | 1,315 | null |
Section: Genetic, molecular and cellular causes > Gene expression robustness. During embryonic development, gene expression must be tightly controlled in time and space in order to give rise to fully functional organs. Developing organisms must therefore deal with the random perturbations resulting from gene expression... | Wikipedia - Robustness (evolution) - Genetic, molecular and cellular causes > Gene expression robustness | 324 | 1,742 | null |
Section: Genetic, molecular and cellular causes > Developmental patterning robustness. Patterning mechanisms such as those described by the French flag model can be perturbed at many levels (production and stochasticity of the diffusion of the morphogen, production of the receptor, stochastic of the signaling cascade, ... | Wikipedia - Robustness (evolution) - Genetic, molecular and cellular causes > Developmental patterning robustness | 217 | 1,141 | null |
Section: Evolutionary consequences. Since organisms are constantly exposed to genetic and non-genetic perturbations, robustness is important to ensure the stability of phenotypes. Also, under mutation-selection balance, mutational robustness can allow cryptic genetic variation to accumulate in a population. While pheno... | Wikipedia - Robustness (evolution) - Evolutionary consequences | 230 | 1,215 | null |
Section: Evolutionary consequences > Emergent mutational robustness. Natural selection can select directly or indirectly for robustness. When mutation rates are high and population sizes are large, populations are predicted to move to more densely connected regions of neutral network as less robust variants have fewer ... | Wikipedia - Robustness (evolution) - Evolutionary consequences > Emergent mutational robustness | 155 | 846 | null |
Section: Evolutionary consequences > Robustness and evolvability. Mutational robustness has been thought to have a negative impact on evolvability because it reduces the mutational accessibility of distinct heritable phenotypes for a single genotype and reduces selective differences within a genetically diverse populat... | Wikipedia - Robustness (evolution) - Evolutionary consequences > Robustness and evolvability | 332 | 1,716 | null |
Section: Inducing scleraxis expression. The syndetome location within the somite is determined by FGF secreted from the center of the myotome (a collection of embryonic tissue that develops into skeletal muscle)- the FGF then induces the adjacent anterior and posterior sclerotome (a collection of embryonic tissue that ... | Wikipedia - Scleraxis - Inducing scleraxis expression | 292 | 1,372 | null |
Section: Background. bHLH transcription factors have been shown to have a wide array of functions in developmental processes. More precisely, they have critical roles in the control of cellular differentiation, proliferation and regulation of oncogenesis. To date, 242 eukaryotic proteins belonging to the HLH superfamil... | Wikipedia - Scleraxis - Background | 286 | 1,381 | null |
Section: Details. The existence of limits in artificial selection experiments was discussed in the scientific literature in the 1940s or earlier. The most obvious possible cause of reaching a limit (or plateau) when a population is under continued directional selection is that all of the additive-genetic variation (see... | Wikipedia - Selection limits - Details | 322 | 1,606 | null |
A negative relation with Darwinian fitness is a situation in which an allele that is "good" for the trait under directional selection is "bad" with respect to lifetime reproductive success. For example, an allele that tends to confer larger body size might also lead to infertility, thus reducing the ability of individu... | Wikipedia - Selection limits - Details | 346 | 1,725 | null |
Some traits have a natural physical limit beyond which a trait cannot possibly go. For example, replicated selection for the building of small thermoregulatory nests in mice reached a limit at or near zero (i.e., none of the provided cotton was being used to make nests). Similarly, lines of maize selected for low oil o... | Wikipedia - Selection limits - Details | 154 | 765 | null |
Section: Experiments to identify causes of selection limits. Experimental approaches to probe the causes of selection are of two general types, quantitative genetic and functional. The former asks general questions about the genetic architecture of the trait when a limit has been attained (e.g., has narrow-sense herita... | Wikipedia - Selection limits - Experiments to identify causes of selection limits | 207 | 1,128 | null |
Section: Representation. A sequence space is usually laid out as a grid. For protein sequence spaces, each residue in the protein is represented by a dimension with 20 possible positions along that axis corresponding to the possible amino acids. Hence there are 400 possible dipeptides arranged in a 20x20 space but that... | Wikipedia - Sequence space (evolution) - Representation | 161 | 863 | null |
Section: Functional sequences in sequence space. Despite the diversity of protein superfamilies, sequence space is extremely sparsely populated by functional proteins. Most random protein sequences have no fold or function. Enzyme superfamilies, therefore, exist as tiny clusters of active proteins in a vast empty space... | Wikipedia - Sequence space (evolution) - Functional sequences in sequence space | 327 | 1,695 | null |
Article: Sex linkage. Sex linkage describes the sex-specific patterns of inheritance and expression when a gene is present on a sex chromosome (allosome) rather than a non-sex chromosome (autosome). Genes situated on the X-chromosome are thus termed X-linked, and are transmitted by both males and females, while genes s... | Wikipedia - Sex linkage - Summary | 281 | 1,360 | null |
Section: Background. In humans (and mammals in general), biological sex is determined by genetics; however this is not the case for all animals, for instance, the biological sex of some reptiles is environmentally determined, and the sex of some worms is dependent on location. 22 of the 23 pairs of human chromosomes ar... | Wikipedia - Sex linkage - Background | 292 | 1,480 | null |
Section: X-linked dominant inheritance. X-linked dominant inheritance is the pattern by which a trait encoded by an allele on the X-chromosome is passed down through generations, wherefore only one copy of that allele is sufficient for an individual to be affected (dominance). Unlike with X-linked recessive traits, fem... | Wikipedia - Sex linkage - X-linked dominant inheritance | 151 | 676 | null |
Section: X-linked dominant inheritance > Frequency and patterns of inheritance. In X-linked dominant inheritance, the transmission of the gene depends on the genotype of each of the parents. A mother heterozygous for an X-linked dominant trait will be affected, and half of her children (whether female or male) will inh... | Wikipedia - Sex linkage - X-linked dominant inheritance > Frequency and patterns of inheritance | 169 | 828 | null |
Section: X-linked recessive inheritance. X-linked recessive inheritance describes one of the patterns of inheritance of genetic traits or disorders encoded by an allele (version of a gene) situated on the X-chromosome. In X-linked recessive inheritance, females (XX) must have two copies of the allele (homozygous), whil... | Wikipedia - Sex linkage - X-linked recessive inheritance | 335 | 1,518 | null |
Section: X-linked diseases > X-linked dominant diseases > Alport syndrome. Alport syndrome is a genetic disorder that primarily affects the kidneys by damaging the glomeruli, which are tiny filtering units inside the kidneys. It is caused by inherited mutations in the COL4A3, COL4A4, and COL4A5 genes, which are respons... | Wikipedia - Sex linkage - X-linked diseases > X-linked dominant diseases > Alport syndrome | 346 | 1,622 | null |
Section: X-linked diseases > X-linked dominant diseases > Fragile X syndrome. Fragile X syndrome is a genetic neurodevelopmental disorder caused by a CGG trinucleotide repeat expansion in the FMR1 gene on the X chromosome. It is inherited in an X-linked dominant pattern and is the most common known inherited genetic ca... | Wikipedia - Sex linkage - X-linked diseases > X-linked dominant diseases > Fragile X syndrome | 325 | 1,595 | null |
Section: X-linked diseases > X-linked dominant diseases > Rett syndrome. Rett syndrome is a severe neurodevelopmental disorder that primarily affects females, with a prevalence of approximately 1 in 8,500. It is caused by mutations in the MECP2 gene located on the X chromosome and is inherited in an X-linked dominant p... | Wikipedia - Sex linkage - X-linked diseases > X-linked dominant diseases > Rett syndrome | 349 | 1,788 | null |
Section: X-linked diseases > X-linked dominant diseases > X-linked hypophosphatemia (vitamin D resistant rickets). X-linked hypophosphatemia is a rare genetic form of rickets caused by mutations in the PHEX gene on the X chromosome. Unlike nutritional rickets, X-linked hypophosphatemia does not respond to vitamin D sup... | Wikipedia - Sex linkage - X-linked diseases > X-linked dominant diseases > X-linked hypophosphatemia (vitamin D resistant rickets) | 341 | 1,502 | null |
Section: X-linked diseases > X-linked recessive diseases. The incidence of X-linked recessive conditions in females is the square of that in males. For example, if 1 in 20 males in a human population are red–green color blind, then 1 in 400 females in the population are expected to be color-blind (1/20)*(1/20). Example... | Wikipedia - Sex linkage - X-linked diseases > X-linked recessive diseases | 199 | 774 | null |
Section: X-linked diseases > X-linked recessive diseases > Duchenne muscular dystrophy. Duchenne muscular dystrophy is a severe neuromuscular disease causing progressive weakness and damage of muscle tissues, leading to mobility loss and difficulties in daily activities. In a later stage of Duchenne muscular dystrophy,... | Wikipedia - Sex linkage - X-linked diseases > X-linked recessive diseases > Duchenne muscular dystrophy | 300 | 1,369 | null |
Section: X-linked diseases > X-linked recessive diseases > X-linked agammaglobulinemia. X-linked agammaglobulinemia is a primary immunodeficiency disorder that impairs the body’s ability to produce antibodies, which are proteins protecting us from disease-causing antigens, resulting in severe bacterial infections. X-li... | Wikipedia - Sex linkage - X-linked diseases > X-linked recessive diseases > X-linked agammaglobulinemia | 302 | 1,373 | null |
Section: X-linked diseases > X-linked recessive diseases > Red-green colour blindness. Red-green colour blindness is a type of colour vision deficiency caused by a mutation in X-linked genes, affecting cone cells responsible for absorbing red or green light. Primarily affecting males (1 in 12) compared to females (1 in... | Wikipedia - Sex linkage - X-linked diseases > X-linked recessive diseases > Red-green colour blindness | 244 | 1,118 | null |
Section: X-linked diseases > X-linked recessive diseases > Hemophilia A. Haemophilia A is a blood clotting disease caused by a genetic defect in clotting factor VIII. It causes significant susceptibility to both internal and external bleeding. 1 in 5,617 live male births is affected, and the condition primarily affects... | Wikipedia - Sex linkage - X-linked diseases > X-linked recessive diseases > Hemophilia A | 319 | 1,466 | null |
This is a condition that shows a low red blood cell count since the body cannot compensate for the quick degrading cells. Glucose-6-phosphate dehydrogenase is an enzyme that protects red blood cells from oxidative stress caused by reactive oxygen species, it will reduce the amount of ROS accumulation of ROS in the red ... | Wikipedia - Sex linkage - X-linked diseases > X-linked recessive diseases > Hemophilia A | 327 | 1,518 | null |
Section: Y-linked inheritance > The Y chromosome. The Y chromosome is comprised of approximately 59 million base pairs and 200 genes, entailing approximately 66 protein-coding genes. Since only biological males possess the Y chromosome, it is essential in male sexual differentiation, which results in the production of ... | Wikipedia - Sex linkage - Y-linked inheritance > The Y chromosome | 236 | 1,226 | null |
Section: Y-linked inheritance > The SRY gene. The SRY gene, being the sex-determining region of the Y chromosome, gives the genetic information required for the body to code for proteins that are involved in male sexual differentiation. The expression of the SRY gene is regulated via a myriad of transcription factors, ... | Wikipedia - Sex linkage - Y-linked inheritance > The SRY gene | 332 | 1,561 | null |
Section: Y-linked inheritance > Y-linked inheritance. Y-linked inheritance, also known as Holandric inheritance, refers to genes that are inherited via the Y chromosome. In other words, Y-linked inheritance involves genes that are only carried on the Y chromosome, also known as Y-linked genes. Inheritance of Y-linked g... | Wikipedia - Sex linkage - Y-linked inheritance > Y-linked inheritance | 225 | 1,058 | null |
Section: Y-linked inheritance > Y-linked disorders > Overview. The first few Y-linked inheritance cases were recognized in the early 20th century, with initial theories proposing certain traits were passed exclusively from father to son. However, it was not until genetic advancements and cytogenetic techniques that ena... | Wikipedia - Sex linkage - Y-linked inheritance > Y-linked disorders > Overview | 177 | 1,050 | null |
Section: Y-linked inheritance > Y-linked disorders > Hypertrichosis. Hypertrichosis is a genetic condition that results in the excessive growth of hair on a specific area of the body, that is abnormal for the age, sex or race of an individual. Specifically, hypertrichosis centralized to the outer ear, also known as the... | Wikipedia - Sex linkage - Y-linked inheritance > Y-linked disorders > Hypertrichosis | 320 | 1,538 | null |
Section: Y-linked inheritance > Y-linked disorders > Webbed toes. Webbing of the toes is the result of premature arrested development in the fetal stage. The premature arrest of development results in second and third digit fusion of the skin. The Y-linked trait of webbed toes causes a skin connection between the secon... | Wikipedia - Sex linkage - Y-linked inheritance > Y-linked disorders > Webbed toes | 208 | 963 | null |
Section: Sex chromosome aneuploidy. Thus far, this article has discussed the patterns of inheritance of sex-linked genes / traits in diploid organisms with the canonical XX (female) or XY (male) genotype. However, there exists a very small fraction of the human population with aneuploidy (an abnormal number) of the sex... | Wikipedia - Sex linkage - Sex chromosome aneuploidy | 343 | 1,572 | null |
Males with the XXYY genotype exhibit similar but often more severe symptoms to Klinefelter syndrome, and are infertile. It is notable that, while sex chromosome aneuploidy is not an inherited condition (and instead arises due to nondisjunction of the sex chromosomes during meiosis) in individuals with an abnormal numbe... | Wikipedia - Sex linkage - Sex chromosome aneuploidy | 228 | 1,003 | null |
Section: Sex-linkage in animals. Most mammals, including humans, use the XY sex determination system and thus follow the same patterns of sex-linked inheritance discussed herein so long as the sex chromosomes are present in normal ploidy (diploidy). However, patterns of inheritance of sex-linked traits differ in animal... | Wikipedia - Sex linkage - Sex-linkage in animals | 346 | 1,465 | null |
Moreover, the mechanism of dosage compensation in Drosophila is not X-inactivation in females, but the two-fold upregulation of expression of genes encoded on the X-chromosome in males. Much of the scientific knowledge on sex-linked traits was derived from observations and experimental evidence made in non-human animal... | Wikipedia - Sex linkage - Sex-linkage in animals | 219 | 995 | null |
Section: History > Discovery of sex chromosomes. The relationship between sex chromosomes and Mendelian inheritance was first discovered by Nettie Stevens. Steven's was influenced by McClung's work highlighting, that some insect species, the difference in chromosome counts possibly determined whether cells develop into... | Wikipedia - Sex linkage - History > Discovery of sex chromosomes | 216 | 1,126 | null |
Section: History > Discovery of X-linked inheritance. Red-green colour blindness was the first described on paper, in 1794 by John Dalton, who was affected by the disorder himself. However, its recognition of its X-linked inheritance characterisitc was only established later. The X-chromosome was discovered in 1890 by ... | Wikipedia - Sex linkage - History > Discovery of X-linked inheritance | 226 | 1,094 | null |
Article: Sex-chromosome dosage compensation. Dosage compensation is the process by which organisms equalize the expression of genes between members of different biological sexes. Across species, different sexes are often characterized by different types and numbers of sex chromosomes. In order to neutralize the large d... | Wikipedia - Sex-chromosome dosage compensation - Summary | 339 | 1,796 | null |
One example of this is X-inactivation which occurs in humans. The third documented type of gene dose regulatory mechanism is incomplete compensation without balance (sometimes referred to as incomplete or partial dosage compensation). In this system gene expression of sex-specific loci is reduced in the heterogametic s... | Wikipedia - Sex-chromosome dosage compensation - Summary | 276 | 1,319 | null |
Section: Random inactivation of one ♀ X. One logical way to equalize gene expression amongst males and females that follow a XX/XY sex differentiation scheme would be to decrease or altogether eliminate the expression of one of the X chromosomes in an XX, or female, homogametic individual, such that both males and fema... | Wikipedia - Sex-chromosome dosage compensation - Random inactivation of one ♀ X | 336 | 1,758 | null |
Lyon began investigating manipulations of X-linked traits that had phenotypically visible consequences, particularly in mice, whose fur color is a trait intimately linked to the X chromosome. Building on work done by Ohno and his colleagues, Lyon eventually proved that either the maternal or paternal X chromosome is ra... | Wikipedia - Sex-chromosome dosage compensation - Random inactivation of one ♀ X | 314 | 1,529 | null |
By analyzing the differential expression of two existing, viable alleles for the X-linked enzyme glucose-6-phosphate dehydrogenase (G6PD) gene, Beutler observed that the inactivation of the gene was heritable across passaged generations of the cells. This pattern of dosage compensation, caused by random X-inactivation,... | Wikipedia - Sex-chromosome dosage compensation - Random inactivation of one ♀ X | 342 | 1,638 | null |
Random X-inactivation demands that the cell can determine if it contains more than one active X-chromosome before acting to silence any extraneous X-chromosome(s). This process is known as "counting". The exact molecular mechanism of counting is still unknown, but a popular model posits that autosomes produce factors t... | Wikipedia - Sex-chromosome dosage compensation - Random inactivation of one ♀ X | 240 | 1,094 | null |
Section: Two-fold increased transcription of a single ♂ X. Another mechanism common for achieving equal X-related genetic expression between males and females involves two-fold increased transcription of a single male X chromosome. Thus, heterogametic male organisms with one X chromosome may match the level of expressi... | Wikipedia - Sex-chromosome dosage compensation - Two-fold increased transcription of a single ♂ X | 347 | 1,773 | null |
Their studies showed equal levels of [3H]uridine incorporation in the single male X chromosome and the two female X chromosomes. Thus, the investigators concluded that the two-fold increase in the rate of RNA synthesis in the X chromosome of the male relative to those of the female could account for Muller's hypothesiz... | Wikipedia - Sex-chromosome dosage compensation - Two-fold increased transcription of a single ♂ X | 348 | 1,719 | null |
In organisms that use this method of dosage compensation, the presence of one or more X chromosomes must be detected early on in development, as failure to initiate the appropriate dosage compensation mechanisms is lethal. Male specific lethal proteins (MSLs) are a family of four proteins that bind to the X chromosome ... | Wikipedia - Sex-chromosome dosage compensation - Two-fold increased transcription of a single ♂ X | 348 | 1,565 | null |
Section: Decreased transcription of both hermaphroditic Xs by half. Other species that do not follow the previously discussed conventions of XX females and XY males must find alternative ways to equalize X-linked gene expression among differing sexes. For example, in Caenorhabditis elegans (or C. elegans), sex is deter... | Wikipedia - Sex-chromosome dosage compensation - Decreased transcription of both hermaphroditic Xs by half | 299 | 1,404 | null |
This complex is crucial to the condensation and segregation of chromosomes during both meiosis and mitosis. Because data substantiates the theory that dosage compensation in other species is caused by chromatin-wide modifications, many theorize that the DCC in particular functions similar to the condensin complex in it... | Wikipedia - Sex-chromosome dosage compensation - Decreased transcription of both hermaphroditic Xs by half | 350 | 1,585 | null |
Xol-1 expression is tightly regulated during early development, and is considered the most upstream gene in sex determination of C. elegans. In fact, xol-1 is often referred to in the literature as the master sex regulatory gene of C. elegans. XX C. elegans embryos have much lower xol-1 expression than their XO counter... | Wikipedia - Sex-chromosome dosage compensation - Decreased transcription of both hermaphroditic Xs by half | 341 | 1,594 | null |
Section: Other species-specific methods. The ZZ/ZW sex system is used by most birds, as well as some reptiles and insects. In this system the Z is the larger chromosome so the males (ZZ) must silence some genetic material to compensate for the female's (ZW) smaller W chromosome. Instead of silencing the entire chromoso... | Wikipedia - Sex-chromosome dosage compensation - Other species-specific methods | 332 | 1,538 | null |
Section: Other species-specific methods > Birds. The sex chromosomes of birds evolved separately from those of mammals and share very little sequence homology with the XY chromosomes. As such, scientists refer to bird sex chromosomes as a ZW sex-determining system, with males possessing two Z chromosomes, and females p... | Wikipedia - Sex-chromosome dosage compensation - Other species-specific methods > Birds | 324 | 1,575 | null |
Thus, the function of the selective silencing may be to spare dosage compensation of genes crucial for sex determination of homologous pairing. Recent studies are focusing on how epigenetic mechanisms could contribute to dosage compensation in birds, with a particular emphasis on methylation. It is already known that s... | Wikipedia - Sex-chromosome dosage compensation - Other species-specific methods > Birds | 312 | 1,418 | null |
Section: Other species-specific methods > Monotremes. Monotremes are a class of basal mammals that also lay eggs. They are an order of mammals that includes platypuses and four species of echidna, all of which are egg-laying mammals. While monotremes use an XX/XY system, unlike other mammals, monotremes have more than ... | Wikipedia - Sex-chromosome dosage compensation - Other species-specific methods > Monotremes | 315 | 1,376 | null |
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