Often symptoms are milder in mosaic cases, with regular male secondary sex characteristics and testicular volume even falling within typical adult ranges. [44] 3.1% of infertile males have Klinefelter syndrome. Nondisjunction in meiosis 1 vs meiosis 2. Change ), You are commenting using your Facebook account. The Klinefelter-Reifenstein-Albright syndrome. Key Words: Klinefelter syndrome, spermatogenesis, meiosis, sperm aneuploidy, TESE Absence of paternal X or Y, or mosaic, haploinsufficiency of SHOX gene (Xpterp22.32) Turner's Syndrome 45,X Recurrence Risk. Although, this figure may be underestimated due to different chromosomal mosaicism levels in different tissues. Most cases are caused by nondisjunction errors in paternal meiosis I. Note how both chromosomes are off to one side in nondisjunction rather than evenly on both sides. Klinefelter's syndrome, XXY males, can occur due to nondisjunction of X chromosomes during prophase of meiosis I in females. ... (Turner syndrome), female with three X chromosomes (Trisomy X), male with XXY (Klinefelter syndrome), or male with XYY (XYY syndrome). Variants of Klinefelter syndrome (such as 48,XXXY, 49,XXXXY) are much rarer, occurring in 1 in 50,000 to 1 in 85,000 or fewer newborns. This unde… People typically have 46 chromosomes in each cell, two of which are the sex chromosomes. An individual with the karyotype 48, XYYY would have how many Barr bodies? The reason maternal non-disjunction during meiosis II can produce XXY offspring. • This means that the individual has a trisomy (3 – 2lst chromosomes). This is asked in They then separate again during meiosis 2. [32][33], The extra chromosome is retained because of a nondisjunction event during paternal meiosis I, maternal meiosis I, or maternal meiosis II (gametogenesis). They may have less muscle control and coordination than other boys of their age. Considering the names of all three researchers, it is sometimes also called Klinefelter–Reifenstein–Albright syndrome. [6] XXY males appear to have a higher risk of breast cancer than typical, but still lower than that of females. Fertilizing a double X egg with a normal sperm also produces an XXY offspring (Klinefelter).[34]. Down’s Syndrome • Caused by non-disjunction of the 21st chromosome. [6] Enlarged breasts may be removed by surgery. Monosomy for autosomes is usually lethal in humans and other animals. Change ). Approximately 15–20%[38] of males with KS may have a mosaic 47,XXY/46,XY constitutional karyotype and varying degrees of spermatogenic failure. Often it is only at pubertythat these symptoms are noticed. An egg with 22 chromosomes that is fertilized by a normal sperm will result in . Click card to see definition . Therefore, depending on the type of mutation, its effect varies. 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 [1] Sometimes, symptoms are more prominent and may include weaker muscles, greater height, poor coordination, less body hair, breast growth, and less interest in sex. [6] About half of affected males have a chance of fathering children with the help of assisted reproductive technology, but this is expensive and not risk free. Every male inherits an x chromosome from their mother and a y chromosome form their father making an xy male. 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. One of the eggs from such a meiosis could receive both X chromosomes, and the other would receive no X chromosomes. Some studies suggest that maternal age is a contributing factor to parental nondisjunction. Robert S. Sparkes, Barbara F. Crandall, in Fetal-Placental Disorders, 1972. ", Eunice Kennedy Shriver National Institute of Child Health and Human Development, "How many people are affected by or at risk for Klinefelter syndrome (KS)? Second, our recent study has provided clear and strong evidence that non-disjunctions of sex chromosomes during meiosis I and II of normal testicular 46-XY spermatogonia/primary spermatocytes do not occur in men with non-mosaic Klinefelter’s syndrome (Yamamoto et al., 2002). [29] Also, delays in motor development may occur, which can be addressed through occupational and physical therapies. ( Log Out /  An 11-year-old patient with incomplete testicular feminization and a 47,XXY karyotype is described. [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. An individual with an error in chromosome number is described as aneuploid, a term that includes monosomy (loss of one chromosome) or trisomy(gain of an extraneous chromosome). [32][51][52][53] However, it is estimated that only 25% of the individuals with Klinefelter syndrome are diagnosed throughout their lives. [30] XXY males may sit up, crawl, and walk later than other infants; they may also struggle in school, both academically and with sports. In 1959, these men with Klinefelter syndrome were discovered to have an extra X chromosome (genotype XXY) instead of the usual male sex complement (genotype XY). This preview shows page 1 out of 1 page. [17] See also Triple X syndrome. Down Syndrome and Maternal Age. [9], The genetic variation is irreversible, thus there is no causal therapy. As you will recall from Figure … : Fill in all possibilities of the nondisjunction events for a particular syndrome could originate. Klinefelter Syndrome is seen in males with an extra X chromosomes. We have not suggested that only spermatocytes with an XX bivalent and a Y univalent are capable of entering meiosis. Nondisjunction occurs when homologous chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate during meiosis. 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. [16], As babies and children, XXY males may have weaker muscles and reduced strength. Nondisjunction in meiosis leads to a loss of a chromosome (monosomy) or extra single chromosome (trisomy). If these eggs are subsequently fertilized with normal sperm, various sex chromosome aneuploidies could occur: Another mechanism for retaining the extra chromosome is through a nondisjunction event during meiosis II in the egg. "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. Even if a cell divides normally in meiosis I, nondisjunction can still occur in the second round of meiosis, meiosis II. Nondisjunction means that a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell. Nondisjunction may occur during meiosis I or meiosis II. What effects might result? Patients with klinefelters have an extra x chromosome and are thus XXY males. The diagram below shows the proper disjunction and nondisjunction in anaphase. An estimated 50% of Klinefelter’s cases are a result of maternal meiotic errors. a) Nondisjunction at meiosis I in the mother. [11] Furthermore, Klinefelter syndrome can be diagnosed as a coincidental prenatal finding in the context of invasive prenatal diagnosis (amniocentesis, chorionic villus sampling). Homologous chromosomes Chiasma Recombinant chromatids Sinauer Associates, Inc 820 0.18 Diploid Unfertilized egg Haploid Haploid Fertilized egg Diploid . About 10% of KS cases are found by prenatal diagnosis. [6] Testosterone replacement may be used in those who have significantly lower levels. Often, symptoms are subtle and subjects do not realize they are affected. 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. [9] KS is diagnosed by the genetic test known as a karyotype. Accordingly, nondisjunction mutation and translocation mutation are two major types of mutations that occur during cell division. 0%. Because of (primary) hypogonadism, individuals often have a low serum testosterone level, but high serum follicle-stimulating hormone and luteinizing hormone levels. The diagram below further shows the process of nondisjunction replication in meiosis 1 and 2. An XX egg is produced, which when fertilized with a Y sperm, yields an XXY offspring. 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. 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. d) Nondisjunction at meiosis II in the father. Klinefelter syndrome is associated with decreased levels of testosterone and is the most common cause of … Hello, the extra X chromosome in the Klinefelter's syndrome is caused by meiotic nondisjunction of chromosomes. At the end of meiosis I, there will be 2 haploid daughter cells, one with n+1 and the other with n-1. An individual with the appropriate number of chromosomes for their species is called euploid; in humans, euploidy corresponds to 22 pairs of autosomes and one pair of sex chromosomes. [1] Often it is only at puberty that these symptoms are noticed. Rarer combinations, such as having five X chromosomes, can also occur. This is not written anywhere in the paper. Tap card to see definition . Occasionally, errors occur during meiosis result in the wrong number of chromosomes ending up in the gamete. a zygote with monosomy. People typically have 46 chromosomes in each cell, two of which are the sex chromosomes. Pathophysiology 2) Wikipedia. [37] These variations are extremely rare. Consider the pedigree below from a human family. Klinefelter’s syndrome (KF) is the most frequent sex chromosome abnormality with an estimated prevalence of 1 in 500 to 1 in 700 newborn males and 1 in 10 in men with azoospermia.While the majority of cases are an XXY genotype, mosaicisms or other aneuploidies can be detected [1]. The primary features are infertility and small poorly functioning testicles. Turner's Syndrome 45,X Cause. Klinefelter syndrome is a sex chromosome disorder in boys and men that results from the presence of an extra X chromosome in cells. Variants of Klinefelter syndrome occur more infrequently; approximately 1 in 50,000 or fewer newborns has a variant of Klinefelter syndrome[2].Most men are diagnosed as adults in the context of male infertility. [4] The syndrome 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. In adults, possible characteristics vary widely and include little to no sign of affectedness, a lanky, youthful build and facial appearance, or a rounded body type with some degree of gynecomastia (increased breast tissue). The homozygous chromosomes then enter the same cell. [44] Testosterone preparations are available in the form of syringes, patches or gel. Which of the following events could not give rise to a Klinefelter male? The incidence of 49,XXXXY is one in 85,000 to 100,000 male births. Some males with KS have no obvious signs or symptoms while others may have varying degrees of cognitive, social, behavioral, and learning difficulties. The resulting gamete will have an XX chromosome configuration. Okay, first nondisjunction refers to the failure of chromosomes to separate correctly during meiosis or mitosis. [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. The affected male has Klinefelter syndrome, a genetic condition that results when a child is born with XXY chromosomes. In humans, the only survivable monosomy is Turner syndrome, which results in an individual who is monosomic for the X chromosome. This probably occurs most commonly in meiosis, but it may occur in mitosis to produce a mosaic individual. Females have two X chromosomes (46,XX), and males have one X and one Y chromosome (46,XY). I was working on this genetics problem: In humans, XXY individuals are males with Klinefelter syndrome. 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. Nondisjunction in Down, Turner, and Klinefelter syndrome p. 80/Task 6e, a, b (preserve this order) Remaining c) and d) - syndromes XXX and supermale – home work, as selfstudy! Klinefelter syndrome (male) Nondisjunction in meiosis of egg or sperm formation Male sex organs but with small testes and the individual is sterile, also has female body characteristics. Klinefelter’s syndrome is a non-disjunction chromosomal condition of the sex chromosomes. About 10% of XXY males have gynecomastia noticeable enough that they may choose to have cosmetic surgery. ", "What are the treatments for symptoms in Klinefelter syndrome (KS)? Change ), You are commenting using your Twitter account. In addition to this linkage, roughly 10% of Klinefelter’s individuals exhibit mosaicism, which means that not all cells present with a trisomy pattern and instead, show a normal XY. Karyotyping – The set of chromosomes in a person with Klinefelter syndrome (Doctor Tipser) The extra chromosome is retained because of a nondisjunction event during paternal or maternal meiosis I (gametogenesis).