Klinefelter syndrome

Klinefelter syndrome, named after Dr. Harry Klinefelter who first identified it, is a chromosomal problem where a person with an xy genotype Biologically a male inherits at least one extra x chromosome and sometimes a few extra ones Having an extra x chromosome makes the testicular cells generate less testosterone Which is a hormone responsible for primary sex characteristics like development of the sex organs as well as secondary sex characteristics like height and body shape It's worth mentioning up front that we're using the term male here rather than boy or man To talk about the biological category of a person sex, rather than a person's gender identity Now in puberty in both male and females the hypothalamus starts to release more gonadotropin releasing hormone Which gets the pituitary gland to release luteinizing hormone and follicle stimulating hormone In males these hormones affect the leydig cells as well as the sertoli cells The leydig cells are in the interstitium of the testes and in response to luteinizing hormone they convert cholesterol into testosterone the testosterone along with follicle stimulating hormone Then stimulates sertoli cells in the seminiferous tubules of the testes to make more sperm to maintain balance, or homeostasis testosterone reduces gonadotropin releasing hormone and luteinizing hormone and sertoli cells release the hormone inhibin which inhibits release of follicle stimulating hormone in Klinefelter syndrome This hormone balance is altered; that extra x-chromosome interrupts the normal function of the sertoli and leydig cells Starting at puberty and continuing throughout life, sertoli and leydig cells don't produce inhibin and testosterone, respectively This means that levels of luteinizing hormone and follicle stimulating hormone increase Less testosterone also suppresses testes maturation and sperm production as well as development of secondary male characteristics in fact each additional x chromosome increases the estrogen to testosterone ratio, making the changes even more striking Klinefelter syndrome develops when a gamete, either sperm or egg, contains at least one extra x chromosome Typically a gamete with 23 chromosomes, including one sex chromosome either x or y develops when parent germ cells undergo the process of meiosis Early on in meiosis the germ cell makes a copy of all of its chromosomes with each chromosome having sister chromatids at that point During the first cellular division called meiosis one the chromosomal pairs are separated in In the second cellular division called theosis to the sister chromatids of a given chromosome are separated In Klinefelter syndrome the sex chromosome pairs which is either xx or xy don't separate in meiosis one in the male or female germ cell and this resulted in two gametes with a pair of x chromosomes and two gametes without x chromosomes The other option is the sister chromatids of the x chromosome don't separate in meiosis two in the female germ cell And this results in one gamete with a pair of x chromosomes one without any and potentially two normal gametes Either way the separation doesn't happen and the end result is a gamete with an extra x chromosome After fertilization a male embryo would then have 47 chromosomes instead of the standard 46 additional failures for sex chromosomes to separate can happen during mitosis in germ cells before they give rise to the gametes if failure also happens during meiosis in these germ cells as they give rise to gametes other xxxxy xxxy and xxyy genotypes that also lead to Klinefelter syndrome can result Including the rare situation where there's an additional y chromosome Symptoms of Klinefelter's syndrome are most apparent around the time of puberty because that's when the reduced testosterone levels are most evident They typically have hypogonadism, or small testicles in a small penis, and are often considered sterile; in other words unable to have children Physically, they're typically tall with long legs, a short torso, broad hips, and gynecomastia or development of breast tissue They usually have less muscle, mass less facial and body hair, weaker bones, and lower energy levels There's also an increased risk of diseases that are more common among women like breast cancer and osteoporosis Finally ,although most boys with Klinefelter syndrome grow up to live as men some develop atypical gender identities and some develop female gender identities Klinefelter syndrome is diagnosed with a karyotype which visualizes each chromosome including the x, y, and extra x chromosomes A karyotype can be done before birth with an amniocentesis or at any time after birth with the blood test Blood tests after puberty can also indicate Klinefelter syndrome Because there are low levels of testosterone and high levels of luteinizing and follicle stimulating hormones Treatment is focused on replacing testosterone through hormone therapy and infertility treatments can make reproduction possible in some cases as well All right as a quick recap Klinefelter Syndrome is a genetic bbnormality in which at least one additional x chromosome is inherited by an xy male as a result of impaired meiosis in the parental gametes This leads to reduce testosterone levels and elevated luteinizing hormone and follicle stimulating hormone all of which causes male sterility and feminized physical features Hey guys, I am lindsay, and I'm a new illustrator for Osmosis, so this is my first video.

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