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83-584: NRY may refer to: Non-recombining Region of the Y chromosome North Riding of Yorkshire (Chapman code) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title NRY . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=NRY&oldid=933022527 " Category : Disambiguation pages Hidden categories: Short description

166-402: A "recombination" is called gene conversion . In the case of the Y chromosomes, the palindromes are not noncoding DNA ; these strings of nucleotides contain functioning genes important for male fertility. Most of the sequence pairs are greater than 99.97% identical. The extensive use of gene conversion may play a role in the ability of the Y chromosome to edit out genetic mistakes and maintain

249-478: A chain is formed during mitosis . The first X chromosome in the chain is also partially homologous with the last Y chromosome, indicating that profound rearrangements, some adding new pieces from autosomes, have occurred in history. Platypus sex chromosomes have strong sequence similarity with the avian Z chromosome , indicating close homology , and the SRY gene so central to sex-determination in most other mammals

332-469: A chromosome survey of 315 male patients at Scotland 's only special security hospital for the developmentally disabled , finding a higher than expected number of patients to have an extra Y chromosome. The authors of this study wondered "whether an extra Y chromosome predisposes its carriers to unusually aggressive behaviour", and this conjecture "framed the next fifteen years of research on the human Y chromosome". Klinefelter syndrome The syndrome

415-720: A consequence of low levels of testosterone. Delays in motor development may occur, which can be addressed through occupational and physical therapies. As teens, males with XXY may develop breast tissue , have weaker bones, and a lower energy level than others. Testicles are affected and are usually less than 2 cm in length (and always shorter than 3.5 cm), 1 cm in width, and 4ml in volume. Those with XXY chromosomes may also have microorchidism (i.e., small testicles). By adulthood, individuals with KS tend to become taller than average, with proportionally longer arms and legs, less-muscular bodies, more belly fat, wider hips, narrower shoulders. Some will show little to no symptomology,

498-434: A double X egg with a normal sperm also produces an XXY or Klinefelter offspring. Another mechanism for retaining the extra chromosome is through a nondisjunction event during meiosis II in the egg. Nondisjunction occurs when sister chromatids on the sex chromosome, in this case an X and an X, fail to separate. An XX egg is produced, which when fertilized with a Y sperm, yields an XXY offspring. This XXY chromosome arrangement

581-469: A female or ambiguous phenotype. In other cases, the SRY gene is copied to the X, leading to birth of an XX male . Many ectothermic vertebrates have no sex chromosomes. If these species have different sexes, sex is determined environmentally rather than genetically. For some species, especially reptiles , sex depends on the incubation temperature. Some vertebrates are hermaphrodites , though hermaphroditic species are most commonly sequential , meaning

664-519: A few orders of fish. The X and Y chromosomes are thought to have evolved from a pair of identical chromosomes, termed autosomes , when an ancestral animal developed an allelic variation (a so-called "sex locus") and simply possessing this allele caused the organism to be male. The chromosome with this allele became the Y chromosome, while the other member of the pair became the X chromosome. Over time, genes that were beneficial for males and harmful to (or had no effect on) females either developed on

747-500: A harder time doing work that involves reading and writing, but most hold jobs and have successful careers. Compared to individuals with a normal number of chromosomes, males affected by Klinefelter syndrome may display behavioral differences. These are phenotypically displayed as higher levels of anxiety and depression, mood dysregulation, impaired social skills, emotional immaturity during childhood, and low frustration tolerance. These neurocognitive disabilities are most likely due to

830-413: A human Y chromosome was shown to contain 62,460,029 base pairs and 41 additional genes . This added 30 million base pairs, but it was discovered that the Y chromosome can vary a lot in size between individuals, from 45.2 million to 84.9 million base pairs. Since almost half of the human Y sequence was unknown before 2022, it could not be screened out as contamination in microbial sequencing projects. As

913-473: A karyotype analysis should be ordered when small testes, infertility, gynecomastia, long arms/legs, developmental delay, speech/language deficits, learning disabilities/academic issues, and/or behavioral issues are present in an individual. The lifespan of individuals with Klinefelter syndrome appears to be reduced by around 2.1 years compared to the general male population. These results are still questioned data, are not absolute, and need further testing. As

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996-752: A lanky, youthful build and facial appearance, or a rounded body type. Gynecomastia (increased breast tissue) in males is common, affecting up to 80% of cases. Approximately 10% of males with XXY chromosomes have gynecomastia noticeable enough that they may choose to have surgery. Individuals with KS are often infertile or have reduced fertility. Advanced reproductive assistance is sometimes possible in order to produce an offspring since approximately 50% of males with Klinefelter syndrome can produce sperm . Some degree of language learning or reading impairment may be present, and neuropsychological testing often reveals deficits in executive functions , although these deficits can often be overcome through early intervention. It

1079-418: A lower bound on the total number of human protein-coding genes. In general, the human Y chromosome is extremely gene poor—it is one of the largest gene deserts in the human genome. Disregarding pseudoautosomal genes, genes encoded on the human Y chromosome include: Diseases linked to the Y chromosome typically involve an aneuploidy , an atypical number of chromosomes. Males can lose the Y chromosome in

1162-442: A male's cells. 47, XYY males have one X chromosome and two Y chromosomes, for a total of 47 chromosomes per cell. Researchers have found that an extra copy of the Y chromosome is associated with increased stature and an increased incidence of learning problems in some boys and men, but the effects are variable, often minimal, and the vast majority do not know their karyotype. In 1965 and 1966 Patricia Jacobs and colleagues published

1245-461: A result, the NCBI RefSeq bacterial genome database mistakenly includes some Y chromosome data. The human Y chromosome is normally unable to recombine with the X chromosome, except for small pieces of pseudoautosomal regions (PARs) at the telomeres (which comprise about 5% of the chromosome's length). These regions are relics of ancient homology between the X and Y chromosomes. The bulk of

1328-566: A shorter life expectancy. In many cases, a cause and effect relationship between the Y chromosome and health outcomes has not been determined, and some propose loss of the Y chromosome could be a "neutral karyotype related to normal aging ". However, a 2022 study showed that mosaic loss of the Y chromosome causally contributes to fibrosis , heart risks , and mortality. Further studies are needed to understand how mosaic Y chromosome loss may contribute to other sex differences in health outcomes, such as how male smokers have between 1.5 and 2 times

1411-463: A single X instead of two Xs ("X0", see Turner syndrome ). There are other variations in which, during embryonic development , the WNT4 gene is activated and/or the SRY gene is damaged leading to birth of an XY female (Swyer syndrome ). A Y chromosome may also be present but fail to result in the development of a male phenotype in individuals with androgen insensitivity syndrome , instead resulting in

1494-490: A skewed ratio between the two Xs. The term " hypogonadism " in XXY symptoms is often misinterpreted to mean "small testicles", when it instead means decreased testicular hormone/endocrine function. Because of (primary) hypogonadism, individuals often have a low serum testosterone level, but high serum follicle-stimulating hormone and luteinizing hormone levels, hypergonadotropic hypogonadism . Despite this misunderstanding of

1577-537: A study of a skeleton found in Bragança , north-eastern Portugal , of a man who died around 1000 AD and was discovered by their investigations to have a 47,XXY karyotype. In 2021, bioarchaeological investigation of the individual buried with the Suontaka sword , previously assumed to be a woman, concluded that person "whose gender identity may well have been non-binary", had Klinefelter syndrome. In many societies,

1660-424: A subset of cells, known as mosaic loss. Mosaic loss is strongly associated with age, and smoking is another important risk factor for mosaic loss. Mosaic loss may be related to health outcomes, indicating that the Y chromosome plays important roles outside of sex determination. Males with a higher percentage of hematopoietic stem cells lacking the Y chromosome have a higher risk of certain cancers and have

1743-439: A well adapted Y chromosome manages to maintain genetic activity by avoiding mutation accumulation, there is no guarantee it will be passed down to the next generation. The population size of the Y chromosome is inherently limited to 1/4 that of autosomes: diploid organisms contain two copies of autosomal chromosomes while only half the population contains 1 Y chromosome. Thus, genetic drift is an exceptionally strong force acting upon

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1826-421: Is 47,XXY/46,XX with clinical features suggestive of KS and male phenotype, but this is very rare. Thus far, only approximately 10 cases of 47,XXY/46,XX have been described in literature. Women typically have two X chromosomes, with half of their X chromosomes switching off early in embryonic development. The same happens with people with Klinefelter's, including in both cases a small proportion of individuals with

1909-502: Is also known to be present in a significant number of men with reduced fertility or reduced sperm count. This results in the person presenting a female phenotype (i.e., is born with female-like genitalia) even though that person possesses an XY karyotype . The lack of the second X results in infertility. In other words, viewed from the opposite direction, the person goes through defeminization but fails to complete masculinization . The cause can be seen as an incomplete Y chromosome:

1992-801: Is apparently not involved in platypus sex-determination. The human Y chromosome is composed of about 62 million base pairs of DNA , making it similar in size to chromosome 19 and represents almost 2% of the total DNA in a male cell . The human Y chromosome carries 693 genes , 107 of which are protein-coding . However, some genes are repeated, making the number of exclusive protein-coding genes just 42. The Consensus Coding Sequence (CCDS) Project only classifies 63 out of 107 genes, though CCDS estimates are often considered lower bounds due to their conservative classification strategy. All single-copy Y-linked genes are hemizygous (present on only one chromosome) except in cases of aneuploidy such as XYY syndrome or XXYY syndrome . Traits that are inherited via

2075-529: Is defined by the presence of at least one extra X chromosome in addition to a Y chromosome , yielding a total of 47 or more chromosomes rather than the usual 46. Klinefelter syndrome occurs randomly. The extra X chromosome comes from the father and mother nearly equally. An older mother may have a slightly increased risk of a child with KS. The syndrome is diagnosed by the genetic test known as karyotyping . Klinefelter syndrome has different manifestations and these will vary from one patient to another. Among

2158-456: Is different from Wikidata All article disambiguation pages All disambiguation pages Y chromosome#Non-combining region of Y .28NRY.29 The Y chromosome is one of two sex chromosomes in therian mammals and other organisms . Along with the X chromosome , it is part of the XY sex-determination system , in which the Y is the sex-determining chromosome because the presence of

2241-509: Is either no longer shrinking or is shrinking at a much slower rate than the 4.6 genes per million years estimated by the linear extrapolation model. The human Y chromosome is particularly exposed to high mutation rates due to the environment in which it is housed. The Y chromosome is passed exclusively through sperm , which undergo multiple cell divisions during gametogenesis . Each cellular division provides further opportunity to accumulate base pair mutations. Additionally, sperm are stored in

2324-713: Is estimated that 10% of those with Klinefelter syndrome are autistic . Additional abnormalities may include impaired attention, reduced organizational and planning abilities, deficiencies in judgment (often presented as a tendency to interpret non-threatening stimuli as threatening), and dysfunctional decision processing. The overall IQ tends to be lower than average. Language milestones may also be delayed, particularly when compared to other people their age. Between 25% and 85% of males with XXY have some kind of language problem, such as delay in learning to speak, trouble using language to express thoughts and needs, problems reading, and trouble processing what they hear. They may also have

2407-421: Is not an aneuploidy of the Y chromosome, but a condition of having an extra X chromosome, which usually results in defective postnatal testicular function. The mechanism is not fully understood; it does not seem to be due to direct interference by the extra X with expression of Y genes. 47, XYY syndrome (simply known as XYY syndrome) is caused by the presence of a single extra copy of the Y chromosome in each of

2490-626: Is one in 85,000 to 100,000 male births. These variations are extremely rare. Additional chromosomal material can contribute to cardiac, neurological, orthopedic, urinogenital and other anomalies. Thirteen cases of individuals with a 47,XXY karyotype and a female phenotype have been described. Approximately 15–20% of males with KS may have a mosaic 47,XXY/46,XY constitutional karyotype and varying degrees of spermatogenic failure. Often, symptoms are milder in mosaic cases, with regular male secondary sex characteristics and testicular volume even falling within typical adult ranges. Another possible mosaicism

2573-663: Is one of the most common genetic variations from the XY karyotype, occurring in approximately one in 500 live male births. In mammals with more than one X chromosome, the genes on all but one X chromosome are not expressed; this is known as X inactivation . This happens in XXY males, as well as normal XX females. However, in XXY males, a few genes located in the pseudoautosomal regions of their X chromosomes have corresponding genes on their Y chromosome and are capable of being expressed. The condition 48, XXYY or 48, XXXY occurs in one in 18,000–50,000 male births. The incidence of 49, XXXXY

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2656-479: Is retained because of a nondisjunction event during paternal meiosis I , maternal meiosis I, or maternal meiosis II , also known as gametogenesis . The relevant nondisjunction in meiosis I occurs when homologous chromosomes, in this case the X and Y or two X sex chromosomes, fail to separate, producing a sperm with an X and a Y chromosome or an egg with two X chromosomes. Fertilizing a normal (X) egg with this sperm produces an XXY or Klinefelter offspring. Fertilizing

2739-594: Is sufficient as test material. In the past, the observation of the Barr body was common practice, as well. To investigate the presence of a possible mosaicism , analysis of the karyotype using cells from the oral mucosa is performed. Physical characteristics of a Klinefelter syndrome can be tall stature, low body hair, and occasionally an enlargement of the breast. Usually, a small testicle volume of 1–5 ml per testicle (standard values: 12–30 ml) occurs. During puberty and adulthood, low testosterone levels with increased levels of

2822-419: Is the entropy rate of the Y chromosome. Whereas all other chromosomes in the human genome have entropy rates of 1.5–1.9 bits per nucleotide (compared to the theoretical maximum of exactly 2 for no redundancy), the Y chromosome's entropy rate is only 0.84. From the definition of entropy rate , the Y chromosome has a much lower information content relative to its overall length, and is more redundant. Even if

2905-594: Is the conservation of the integrity of the genome, a proposal consistent with the idea that meiosis is an adaptation for repairing DNA damage . Without the ability to recombine during meiosis , the Y chromosome is unable to expose individual alleles to natural selection. Deleterious alleles are allowed to "hitchhike" with beneficial neighbors, thus propagating maladapted alleles into the next generation. Conversely, advantageous alleles may be selected against if they are surrounded by harmful alleles (background selection). Due to this inability to sort through its gene content,

2988-419: The pseudoautosomal region (PAR). The PAR undergoes frequent recombination between the X and Y chromosomes, but recombination is suppressed in other regions of the Y chromosome. These regions contain sex-determining and other male-specific genes. Without this suppression, these genes could be lost from the Y chromosome from recombination and cause issues such as infertility. The lack of recombination across

3071-484: The American Association for Klinefelter Syndrome Information and Support (AAKSIS), have played a crucial role in promoting understanding and improving the quality of life for affected individuals. This syndrome, evenly distributed in all ethnic groups , has a prevalence of approximately four subjects per every 10,000 (0.04%) males in the general population. However, it is estimated that only 25% of

3154-415: The X and Y is still possible. Because the male specific region is very small and contains no essential genes, it is even possible to artificially induce XX males and YY females to no ill effect. Monotremes like platypuses possess four or five pairs of XY sex chromosomes, each pair consisting of sex chromosomes with homologous regions. The chromosomes of neighboring pairs are partially homologous, such that

3237-458: The X chromosome, and people with two X chromosomes are typically only carriers rather than affected by these X-linked recessive conditions. Klinefelter syndrome is not an inherited condition. The extra X chromosome comes from the mother in approximately 50% of the cases. Maternal age is the only known risk factor. Women at 40 years have a four-times-higher risk of a child with Klinefelter syndrome than women aged 24 years. The extra chromosome

3320-668: The Y chromosome are called Y-linked traits, or holandric traits (from Ancient Greek ὅλος hólos , "whole" + ἀνδρός andrós , "male"). At the end of the Human Genome Project (and after many updates) almost half of the Y chromosome remained un-sequenced even in 2021; a different Y chromosome from the HG002 (GM24385) genome was completely sequenced in January 2022 and is included in the new "complete genome" human reference genome sequence, CHM13. The complete sequencing of

3403-525: The Y chromosome causes offspring produced in sexual reproduction to be of male sex . In mammals, the Y chromosome contains the SRY gene, which triggers development of male gonads . The Y chromosome is passed only from male parents to male offspring. The Y chromosome was identified as a sex-determining chromosome by Nettie Stevens at Bryn Mawr College in 1905 during a study of the mealworm Tenebrio molitor . Edmund Beecher Wilson independently discovered

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3486-410: The Y chromosome contains a gene, SRY , which triggers embryonic development as a male. The Y chromosomes of humans and other mammals also contain other genes needed for normal sperm production. There are exceptions, however. Among humans, some males are born two Xs and a Y ("XXY", see Klinefelter syndrome ), one X and two Ys (see XYY syndrome ). Some females have three Xs ( Trisomy X ), and some have

3569-441: The Y chromosome does not trigger male development. Instead, sex is determined by the number of X chromosomes. The D. melanogaster Y chromosome does contain genes necessary for male fertility. So XXY D. melanogaster are female, and D. melanogaster with a single X (X0), are male but sterile. There are some species of Drosophila in which X0 males are both viable and fertile. Other organisms have mirror image sex chromosomes: where

3652-483: The Y chromosome is particularly prone to the accumulation of "junk" DNA . Massive accumulations of retrotransposable elements are scattered throughout the Y. The random insertion of DNA segments often disrupts encoded gene sequences and renders them nonfunctional. However, the Y chromosome has no way of weeding out these "jumping genes". Without the ability to isolate alleles, selection cannot effectively act upon them. A clear, quantitative indication of this inefficiency

3735-452: The Y chromosome or were acquired by the Y chromosome through the process of translocation . Until recently, the X and Y chromosomes in mammals were thought to have diverged around 300 million years ago. However, research published in 2008 analyzing the platypus genome suggested that the XY sex-determination system would not have been present more than 166 million years ago, when monotremes split from other mammals. This re-estimation of

3818-436: The Y chromosome, such as most species of Nematodes. However, in order for the complete elimination of Y to occur, it was necessary to develop an alternative way of determining sex (for example, by determining sex by the ratio of the X chromosome to autosomes), and any genes necessary for male function had to be moved to other chromosomes. In the meantime, modern data demonstrate the complex mechanisms of Y chromosome evolution and

3901-456: The Y chromosome, which does not recombine, is called the "NRY", or non-recombining region of the Y chromosome. Single-nucleotide polymorphisms (SNPs) in this region are used to trace direct paternal ancestral lines. More specifically, PAR1 is at 0.1–2.7 Mb. PAR2 is at 56.9–57.2 Mb. The non-recombining region (NRY) or male-specific region (MSY) sits between. Their sizes is now known perfectly from CHM13: 2.77 Mb and 329.5 kb. Until CHM13

3984-472: The Y chromosome. Through sheer random assortment, an adult male may never pass on his Y chromosome if he only has female offspring. Thus, although a male may have a well adapted Y chromosome free of excessive mutation, it may never make it into the next gene pool. The repeat random loss of well-adapted Y chromosomes, coupled with the tendency of the Y chromosome to evolve to have more deleterious mutations rather than less for reasons described above, contributes to

4067-422: The age of the therian XY system is based on the finding that sequences that are on the X chromosomes of marsupials and eutherian mammals are not present on the autosomes of platypus and birds. The older estimate was based on erroneous reports that the platypus X chromosomes contained these sequences. Most chromosomes recombine during meiosis. However, in males, the X and Y pair in a shared region known as

4150-457: The alternate route of crossover recombination. The Y-Y gene conversion rate in humans is about 1.52 x 10 conversions/base/year. These gene conversion events may reflect a basic function of meiosis, that of conserving the integrity of the genome. According to some theories, in the terminal stages of the degeneration of the Y chromosome, other chromosomes may increasingly take over genes and functions formerly associated with it and finally, within

4233-511: The ancestral sex chromosomes and autosomes . Modern data cast doubt on the hypothesis that the Y-chromosome will disappear. This conclusion was reached by scientists who studied the Y chromosomes of rhesus monkeys. When genomically comparing the Y chromosome of rhesus monkeys and humans, scientists found very few differences, given that humans and rhesus monkeys diverged 30 million years ago. Outside of mammals, some organisms have lost

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4316-487: The condition; they have friends, families, and normal social relationships. Nonetheless, some individuals may experience social and emotional problems due to problems in childhood. They show a lower sex drive and low self-esteem, in most cases due to their feminine physical characteristics. Those with XXY are more likely than others to have certain health problems, such as autoimmune disorders , breast cancer , venous thromboembolic disease , and osteoporosis . Nonetheless,

4399-493: The data in PAR1 and PAR2 was just copied over from X chromosome. The following are some of the gene count estimates of human Y chromosome. Because researchers use different approaches to genome annotation their predictions of the number of genes on each chromosome varies (for technical details, see gene prediction ). Among various projects, CCDS takes an extremely conservative strategy. So CCDS's gene number prediction represents

4482-660: The fact that the disappearance of the Y chromosome is not guaranteed. Fisher's principle outlines why almost all species using sexual reproduction have a sex ratio of 1:1. W. D. Hamilton gave the following basic explanation in his 1967 paper on "Extraordinary sex ratios", given the condition that males and females cost equal amounts to produce: Many groups of organisms in addition to therian mammals have Y chromosomes, but these Y chromosomes do not share common ancestry with therian Y chromosomes. Such groups include monotremes, Drosophila , some other insects, some fish, some reptiles, and some plants. In Drosophila melanogaster ,

4565-453: The fate of all non-recombining sex chromosomes, due to three common evolutionary forces: high mutation rate , inefficient selection , and genetic drift . With a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest-evolving parts of the human genome . However, these changes have been limited to non-coding sequences and comparisons of the human and chimpanzee Y chromosomes (first published in 2005) show that

4648-399: The framework of this theory, the Y chromosome disappears entirely, and a new sex-determining system arises. Several species of rodent in the sister families Muridae and Cricetidae have reached a stage where the XY system has been modified, in the following ways: Outside of the rodents, the black muntjac , Muntiacus crinifrons , evolved new X and Y chromosomes through fusions of

4731-404: The genetic variation is irreversible, no causal therapy is available. From the onset of puberty, the existing testosterone deficiency can be compensated by appropriate hormone-replacement therapy. Testosterone preparations are available in the form of syringes, patches, or gel. If gynecomastia is present, the surgical removal of the breast may be considered for psychological benefits and to reduce

4814-416: The highly oxidative environment of the testis , which encourages further mutation. These two conditions combined put the Y chromosome at a greater opportunity of mutation than the rest of the genome. The increased mutation opportunity for the Y chromosome is reported by Graves as a factor 4.8. However, her original reference obtains this number for the relative mutation rates in male and female germ lines for

4897-536: The homogeneous sex is the male, with two Z chromosomes, and the female is the heterogeneous sex with a Z chromosome and a W chromosome. For example, the ZW sex-determination system is found in birds , snakes , and butterflies ; the females have ZW sex chromosomes, and males have ZZ sex chromosomes. There are some species, such as the Japanese rice fish , in which the XY system is still developing and cross over between

4980-409: The human Y chromosome has not lost any genes since the divergence of humans and chimpanzees between 6–7 million years ago. Additionally, a scientific report in 2012 stated that only one gene had been lost since humans diverged from the rhesus macaque 25 million years ago. These facts provide direct evidence that the linear extrapolation model is flawed and suggest that the current human Y chromosome

5063-463: The integrity of the relatively few genes it carries. In other words, since the Y chromosome is single, it has duplicates of its genes on itself instead of having a second, homologous, chromosome. When errors occur, it can use other parts of itself as a template to correct them. Findings were confirmed by comparing similar regions of the Y chromosome in humans to the Y chromosomes of chimpanzees , bonobos and gorillas . The comparison demonstrated that

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5146-439: The lineage leading to humans. The observation that the Y chromosome experiences little meiotic recombination and has an accelerated rate of mutation and degradative change compared to the rest of the genome suggests an evolutionary explanation for the adaptive function of meiosis with respect to the main body of genetic information. Brandeis proposed that the basic function of meiosis (particularly meiotic recombination)

5229-451: The majority of the Y chromosome makes it a useful tool in studying human evolution , since recombination complicates the mathematical models used to trace ancestries. By one estimate, the human Y chromosome has lost 1,393 of its 1,438 original genes over the course of its existence, and linear extrapolation of this 1,393-gene loss over 300 million years gives a rate of genetic loss of 4.6 genes per million years. Continued loss of genes at

5312-483: The microscope and only take on a well-defined shape during mitosis . This shape is vaguely X-shaped for all chromosomes. It is entirely coincidental that the Y chromosome, during mitosis , has two very short branches which can look merged under the microscope and appear as the descender of a Y-shape. Most therian mammals have only one pair of sex chromosomes in each cell. Males have one Y chromosome and one X chromosome , while females have two X chromosomes. In mammals,

5395-731: The most common cause of spontaneous abortion. Generally, the severity of the malformations is proportional to the number of extra X chromosomes present in the karyotype. For example, patients with 49 chromosomes (XXXXY) have a lower IQ and more severe physical manifestations than those with 48 chromosomes (XXXY). As babies and children, those with XXY chromosomes may have lower muscle tone and reduced strength. They may sit up, crawl, and walk later than other infants. An average KS child will start walking at 19 months of age. They may also have less muscle control and coordination than other children of their age. During puberty, KS subjects show less muscular body, less facial and body hair, and broader hips as

5478-411: The names of all three researchers, it is sometimes also called Klinefelter–Reifenstein–Albright syndrome. In 1956, Klinefelter syndrome was found to result from an extra chromosome. Plunkett and Barr found the sex chromatin body in cell nuclei of the body. This was further clarified as XXY in 1959 by Patricia Jacobs and John Anderson Strong . The first published report of a man with a 47,XXY karyotype

5561-402: The organism switches sex, producing male or female gametes at different points in its life, but never producing both at the same time. This is opposed to simultaneous hermaphroditism, where the same organism produces male and female gametes at the same time. Most simultaneous hermaphrodite species are invertebrates, and among vertebrates, simultaneous hermaphroditism has only been discovered in

5644-508: The pituitary hormones FSH and LH in the blood can indicate the presence of Klinefelter syndrome. A spermiogram can also be part of the further investigation. Often, an azoospermia is present, or rarely an oligospermia. Furthermore, Klinefelter syndrome can be diagnosed as a coincidental prenatal finding in the context of invasive prenatal diagnosis (amniocentesis, chorionic villus sampling). Approximately 10% of KS cases are found by prenatal diagnosis . The symptoms of KS are often variable, so

5727-587: The presence of the extra X chromosome, as indicated by studies carried out on animal models carrying an extra X chromosome. In 1995, a scientific study evaluated the psychosocial adaptation of 39 adolescents with sex chromosome abnormalities. It demonstrated that males with XXY tend to be quiet, shy and undemanding; they are less self-confident, less active, and more helpful and obedient than other children their age. They may struggle in school and sports, meaning they may have more trouble "fitting in" with other kids. As adults, they live lives similar to others without

5810-431: The presence or absence of the Y chromosome. In the early 1920s, Theophilus Painter determined that X and Y chromosomes determined sex in humans (and other mammals). The chromosome was given the name "Y" simply to follow on from Henking's "X" alphabetically. The idea that the Y chromosome was named after its similarity in appearance to the letter "Y" is mistaken. All chromosomes normally appear as an amorphous blob under

5893-482: The primary features are infertility and small, poorly functioning testicles. Often, symptoms may be subtle and many people do not realize they are affected. In other cases, symptoms are more prominent and may include weaker muscles, greater height, poor motor coordination, less body hair, gynecomastia (breast growth), and low libido. In the majority of the cases, these symptoms are noticed only at puberty . Chromosomal abnormalities, including Klinefelter syndrome, are

5976-435: The rate of 4.6 genes per million years would result in a Y chromosome with no functional genes – that is the Y chromosome would lose complete function – within the next 10 million years, or half that time with the current age estimate of 160 million years. Comparative genomic analysis reveals that many mammalian species are experiencing a similar loss of function in their heterozygous sex chromosome. Degeneration may simply be

6059-523: The risk of breast cancer is still below the normal risk for women. These patients are also more prone to develop cardiovascular disease due to the predominance of metabolic abnormalities such as dyslipidemia and type 2 diabetes . It has not been demonstrated that hypertension is related with KS. In contrast to these potentially increased risks, rare X-linked recessive conditions are thought to occur less frequently in those with XXY than in those without, since these conditions are transmitted by genes on

6142-641: The risk of breast cancer. The use of behavioral therapy can mitigate any language disorders, difficulties at school, and socialization. An approach by occupational therapy is useful in children, especially those who have dyspraxia . Methods of reproductive medicine, such as intracytoplasmic sperm injection (ICSI) with previously conducted testicular sperm extraction (TESE), have led to men with Klinefelter syndrome producing biological offspring. By 2010, over 100 successful pregnancies have been reported using in vitro fertilization technology with surgically removed sperm material from men with KS. The syndrome

6225-460: The risk of non-respiratory cancers as female smokers. Potential countermeasures identified so far include not smoking or stopping smoking and at least one potential drug that "may help counteract the harmful effects of the chromosome loss" is under investigation. Y chromosome microdeletion (YCM) is a family of genetic disorders caused by missing genes in the Y chromosome. Many affected men exhibit no symptoms and lead normal lives. However, YCM

6308-460: The same mechanisms the same year, working with Hemiptera . Stevens proposed that chromosomes always existed in pairs and that the smaller chromosome (now labelled "Y") was the pair of the X chromosome discovered in 1890 by Hermann Henking . She realized that the previous idea of Clarence Erwin McClung , that the X chromosome determines sex, was wrong and that sex determination is, in fact, due to

6391-412: The same phenomenon of gene conversion appeared to be at work more than 5 million years ago, when humans and the non-human primates diverged from each other. Gene conversion tracts formed during meiosis are long, about 2,068 base pairs, and significantly biased towards the fixation of G or C nucleotides (GC biased). The recombination intermediates preceding gene conversion were found to rarely take

6474-428: The species-wide degeneration of Y chromosomes through Muller's ratchet . As has been already mentioned, the Y chromosome is unable to recombine during meiosis like the other human chromosomes; however, in 2003, researchers from MIT discovered a process which may slow down the process of degradation. They found that human Y chromosome is able to "recombine" with itself, using palindrome base pair sequences. Such

6557-482: The symptoms of Klinefelter syndrome have contributed to significant social stigma , particularly due to infertility and gynecomastia. Historically, these traits were often associated with a perceived lack of masculinity , which could result in social ostracism. However, in recent years, increased awareness and advocacy have led to a reduction in stigma, with individuals diagnosed with KS more likely to receive proper medical care and support. Advocacy organizations, such as

6640-434: The term, testicular growth is arrested. Destruction and hyalinization of the seminiferous tubules cause a reduction in the function of Sertoli cells and Leydig cells , leading to decreased production of FSH and testosterone . This results in impaired spermatogenesis and further endocrine dysfunction. The standard diagnostic method is the analysis of the chromosomes' karyotype on lymphocytes . A small blood sample

6723-488: The usual karyotype in these cases is 45X, plus a fragment of Y. This usually results in defective testicular development, such that the infant may or may not have fully formed male genitalia internally or externally. The full range of ambiguity of structure may occur, especially if mosaicism is present. When the Y fragment is minimal and nonfunctional, the child is usually a girl with the features of Turner syndrome or mixed gonadal dysgenesis . Klinefelter syndrome (47, XXY)

6806-485: Was by Patricia Jacobs and John Strong at Western General Hospital in Edinburgh, Scotland , in 1959. This karyotype was found in a 24-year-old man who had signs of KS. Jacobs described her discovery of this first reported human or mammalian chromosome aneuploidy in her 1981 William Allan Memorial Award address. Klinefelter syndrome has been identified in ancient burials. In August 2022, a team of scientists published

6889-476: Was named after American endocrinologist Harry Klinefelter , who in 1942 worked with Fuller Albright and E. C. Reifenstein at Massachusetts General Hospital in Boston, Massachusetts , and first described it in the same year. The account given by Klinefelter came to be known as Klinefelter syndrome as his name appeared first on the published paper, and seminiferous tubule dysgenesis was no longer used. Considering

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