Klinefelter Syndrome is seen in males with an extra X chromosomes. At the moment, scientists do not understand why the pair of chromosomes fails to separate during cell division. [32][51][52][53] However, it is estimated that only 25% of the individuals with Klinefelter syndrome are diagnosed throughout their lives. [21] It has been estimated that 50% of males with Klinefelter syndrome can produce sperm. This happens because of the process of non-disjunction. Abnormal Meiosis and Fertilization Non-disjunction Disorders: • Occur when the homologous chromosomes fail to _____ to opposite poles of the cell during meiosis. The origin of the XXY genotype is most commonly from errors related to nondisjunction in paternal meiosis 1 [3]. [23] Despite this misunderstanding of the term, however, XXY men may also have microorchidism (i.e., small testicles). At the end of meiosis I, there will be 2 haploid daughter cells, one with n+1 and the other with n-1. Down’s Syndrome • Caused by non-disjunction of the 21st chromosome. The trisomy pattern of Klinefelter’s can occur through various errors. Some males with KS have no obvious signs or symptoms while others may have varying degrees of cognitive, social, behavioral, and learning difficulties. An 11-year-old patient with incomplete testicular feminization and a 47,XXY karyotype is described. Once these gametes are fertilized, aneuploidy individuals may result in several syndromes such as Down’s syndrome, Klinefelter syndrome, Turner’s syndrome, etc. In nondisjunction during meiosis 1, the homozygous chromosome fail to pair and exchange genetic material during the metaphase plate. This is similar to the maternal case except that after meiosis I, in one cell will be two YY chromosomes while the other cell will be two XX chromosomes. 1. Klinefelter's syndrome, XXY males, can occur due to nondisjunction of X chromosomes during prophase of meiosis I in females. 2012 by American Society for Reproductive Medicine.) To better understand the consequences let us consider those that affect people. You hear about XX and XY but this is about XXY. [1] Often it is only at puberty that these symptoms are noticed. Pathophysiology 2) Wikipedia. Advanced reproductive assistance is sometimes possible. [5], While no cure is known, a number of treatments may help. Nondisjunction occurs when homologous chromosomes, in this case the … Occasionally, errors occur during meiosis result in the wrong number of chromosomes ending up in the gamete. Possible to have subnormal intelligence Even if a cell divides normally in meiosis I, nondisjunction can still occur in the second round of meiosis, meiosis II. [19] Gynecomastia is present in about a third of affected individuals, a slightly higher percentage than in the XY population. [5] Intelligence is usually normal; however, reading difficulties and problems with speech are more common. Most cases are caused by nondisjunction errors in paternal meiosis I. Fertilizing a double X egg with a normal sperm also produces an XXY offspring (Klinefelter).[34]. It represents the most frequent cause of hypogonadism and infertility in men. Which of the following events could not give rise to a Klinefelter male? [17], During puberty, the physical traits of the syndrome become more evident; because these boys do not produce as much testosterone as other boys, they have a less muscular body, less facial and body hair, and broader hips. Homologous chromosomes Chiasma Recombinant chromatids Sinauer Associates, Inc 820 0.18 Diploid Unfertilized egg Haploid Haploid Fertilized egg Diploid . Müller U(1), Schneider NR, Marks JF, Kupke KG, Wilson GN. • This means that the individual has a trisomy (3 – 2lst chromosomes). [14] Mice can also have the XXY syndrome, making them a useful research model. Change ), You are commenting using your Facebook account. 23 and 24, During meiosis I in an individual with Klinefelter syndrome, two sex chromosomes will migrate to one daughter cell and one sex chromosome will migrate to the other daughter cell. ( Log Out /  Half of the gametes from nondisjunction during meiosis II will have normal chromosome number. If these eggs are subsequently fertilized with normal sperm, various sex chromosome aneuploidies could occur: Sometimes, symptoms are more evident and may include weaker muscles, greater height, poor coordination, less body hair, breast growth, and less interest in sex. ( Log Out /  Create a free website or blog at WordPress.com. [6] XXY males appear to have a higher risk of breast cancer than typical, but still lower than that of females. [3] The primary features are infertility and small poorly functioning testicles. It is estimated that 1 in every 500 to 1,000 newborn males has an extra X chromosome, making Klinefelter syndrome one of the most common chromosomal disorders seen among newborns. In 1942, Klinefelter et al published a report on 9 men who had enlarged breasts, sparse facial and body hair, small testes, and an inability to produce sperm. [44] Testosterone preparations are available in the form of syringes, patches or gel. I was working on this genetics problem: In humans, XXY individuals are males with Klinefelter syndrome. Click card to see definition . Fertilizing a normal (X) egg with this sperm produces an XXY offspring (Klinefelter). Question: Nondisjunction M M 31 Exercise 5.2 Errors In Meiosis Can Cause Syndromes Errors In Meiosis Lead To Chromosomal Disorders The Process That Creates Gametes In Human Reproductive Organs Is Called Melosis. Turner syndrome. [6] Testosterone replacement may be used in those who have significantly lower levels. Often there is an azoospermia present, rarely an oligospermia. Some studies suggest that maternal age is a contributing factor to parental nondisjunction. e) All of the … As shown in Figure 1.1 non-disjunction within Meiosis I will result in a two trisomic gametes and two monosomic gametes (as shown on the right side of Figure 1.1). About 10% of KS cases are found by prenatal diagnosis. The explanation for this is because the nondisjunction error occurred after fertilization. In contrast, in other men with non-mosaic Klinefelter’s syndrome, some 47-XXY germ cells may undergo meiosis I and II due to adequate Sertoli cell secretory function. [43], The symptoms of KS are often variable; therefore, 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. Intelligence is usuall… Occasionally, Errors Occur During Meiosis Result In The Wrong Number Of Chromosomes Ending Up In The Gamete. Klinefelter’s syndrome is a non-disjunction chromosomal condition of the sex chromosomes. Nondisjunction is the term used to describe when the genetic material is unevenly distributed between the daughter cells during meiosis I or between the haploid gametes at the end of meiosis II, and is the cause for most chromosomal disorders, including Klinefelter's. [1] Sometimes, symptoms are more evident and may include weaker muscles, greater height, poor coordination, less body hair, breast growth, and less interest in sex. This happens in XXY males, as well as normal XX females. Klinefelter Syndrome: 47,XXY males - 1/600 males - Due to nondisjunction of X chromosomes during meiosis I in females - Male sex organs; unusually small testes whichfail to produce normal levels of testosteroneà breast enlargement (gynaecomastia) and other feminine body characteristic - Patients are taller and thinner than Another mechanism for retaining the extra chromosome is through a nondisjunction event during meiosis II in the egg. a) Nondisjunction at meiosis I in the mother. [41] To investigate the presence of a possible mosaicism, analysis of the karyotype using cells from the oral mucosa is performed. Both of these daughter cells will then go on to divide once more in meiosis II, producing 4 daughter cells, 2 with n+1 and 2 with n-1. Approximately 15–20%[38] of males with KS may have a mosaic 47,XXY/46,XY constitutional karyotype and varying degrees of spermatogenic failure. "The William Allan Memorial Award address: human population cytogenetics: the first twenty-five years", Acute myeloblastic leukemia with maturation, 46,XX testicular disorders of sex development, https://en.wikipedia.org/w/index.php?title=Klinefelter_syndrome&oldid=991327778, Wikipedia indefinitely move-protected pages, Articles with unsourced statements from March 2015, Wikipedia medicine articles ready to translate, Creative Commons Attribution-ShareAlike License, XXY syndrome, Klinefelter's syndrome, Klinefelter-Reifenstein-Albright syndrome, This page was last edited on 29 November 2020, at 13:52. [38] Another possible mosaicism is 47,XXY/46,XX with clinical features suggestive of KS and male phenotype, but this is very rare. The diagram below further shows the process of nondisjunction replication in meiosis 1 and 2. The syndrome is also the main cause of male hypogonadism. Nondisjunction may occur during meiosis I or meiosis II. The 47,XXY karyotype of Klinefelter syndrome spontaneously arises when paired X chromosomes fail to separate (nondisjunction in stage I or II of meiosis, during oogenesis or spermatogenesis). Sometimes, nondisjunction can result in combinations such as 48, XXXY and 49, XXXXY, where there are 3 and 4 X chromosomes instead of just 2, resulting in more severe and more dangerous variations of Klinefelter's Syndrome. (Fertil Steril 2012;98:253–60. In 1942, Klinefelter et al published a report on 9 men who had enlarged breasts, sparse facial and body hair, small testes, and an inability to produce sperm. Turner's Syndrome 45,X Phenotype. [1], Klinefelter syndrome occurs randomly. This preview shows page 1 out of 1 page. They may have less muscle control and coordination than other boys of their age. : Fill in all possibilities of the nondisjunction events for a particular syndrome could originate. A small blood sample is sufficient as test material. Okay, here we go: For an example, let's keep it simple and just look at the two sex chromosomes. Therefore one of the cells in meiosis wasn't given an X chromosome, and when sexual reproduction occurred, only one X chromosome present in the embryo. Nondisjunction occurs when sister chromatids on the sex chromosome, in this case an X and an X, fail to separate. [57] This karyotype was found in a 24-year-old man who had signs of KS. Down Syndrome and Maternal Age. Thus, the main difference between nondisjunction in meiosis 1 and 2 is nondisjunction in meiosis 1 occurs in homologous chromosomes while nondisjunction in meiosis II occurs in sister chromatids. An XX egg is produced, which when fertilized with a Y sperm, yields an XXY offspring. The XXY chromosome complement, corresponding to one type of Klinefelter syndrome, corresponds to male individuals with small testes, enlarged breasts, and reduced body hair. -The former results in Klinefelter syndrome when fertilized by a Y containing sperm. [31], Maternal age is the only known risk factor. Pathophysiology 2) Wikipedia. On a microscopic scale this means that the egg or sperm contain an extra X chromosome. About 10% of XXY males have gynecomastia noticeable enough that they may choose to have cosmetic surgery. Klinefelter syndrome is a chromosomal aneuploidy characterized by the presence of 1 or more extra X chromosomes in a male karyotype, most commonly leading to karyotype 47,XXY. [50], This syndrome, evenly distributed in all ethnic groups, has a prevalence of one to two subjects per every 1000 males in the general population. This chromosomal abnormality most likely results from a chromosomal non-disjunction during meiosis. [17] See also Triple X syndrome. One of the eggs from such a meiosis could receive both X chromosomes, and the other would receive no X chromosomes. When non-disjunction occurs (assuming it occurs in both divisions), these chromosome arrangements remain the same and two cells are formed. This is what commonly accompanies nondisjunction. 1 NONDISJUNCTION. Klinefelter's syndrome, XXY males, can occur due to nondisjunction of X chromosomes during prophase of meiosis I in females. Sex Cells Haploid cells (sex cells included) are created through… [20], Affected males are often infertile, or have reduced fertility. Maternal meiosis II nondisjunction in a case of 47,XXY testicular feminization. I dont understand why nondisjunction only occured with the mom and how im supposed to distinguish between nondisjunction in meiosis 1 and 2. Nondisjunction in meiosis 1 vs meiosis 2. 21 16 22 IXI 12 18 1 15 c) Nondisjunction in meiosis Il Nondisjunction . Nondisjunction M M 31 Exercise 5.2 Errors in Meiosis Can Cause Syndromes Errors in Meiosis Lead to Chromosomal Disorders The process that creates gametes in human reproductive organs is called melosis. Therefore, nondisjunction accounts for the presence of a trisomy of sex chromosomes. [7], Klinefelter syndrome is one of the most common chromosomal disorders, occurring in one to two per 1,000 live male births. This XXY chromosome arrangement is one of the most common genetic variations from the XY karyotype, occurring in about one in 500 live male births. [1] Symptoms are typically more severe if three or more X chromosomes are present (48,XXXY syndrome or 49,XXXXY syndrome). [3][9] Often, symptoms may be subtle and many people do not realize they are affected. One of the eggs from such a meiosis could receive both X chromosomes, and the other would receive no X chromosomes. Nondisjunction in meiosis 1 vs meiosis 2. ", "What are the treatments for symptoms in Klinefelter syndrome (KS)? 48,XXYY or 48,XXXY occurs in one in 18,000–50,000 male births. [42] During puberty and adulthood, low testosterone levels with increased levels of the pituitary hormones FSH and LH in the blood can indicate the presence of Klinefelter syndrome. Assuming you mean non-disjunction, this refers to chromosome pairs not separating properly during meiosis and therefore, you end up, instead of two sperm with one sex chromosome each, you have one sperm with two sex chromosomes (see below) and one sperm with no sex chromosome at all (which, upon joining with the X of a mother's egg will produce an XO turners syndrome child). An approach by occupational therapy is useful in children, especially those who have dyspraxia. If gynecomastia is present, the surgical removal of the breast may be considered for both the psychological reasons and to reduce the risk of breast cancer. 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