Lecture 3: Num and Struc Abn's Flashcards
Euploidy
Multiples of one complete chromosome complement
Tetraploidy
4N. Seen in spont abortus tissues. Due to post meiotic event and presents as dup of 2N complement most likely due to failure of an early mitotic cleavage in the zygote.
Triploidy
Seen in abortus tissue, due to dispermy or failure in gametogenesis of one of the meiotic divisions.
Aneuploidy. Definition, result, cause.
Gain or loss of C’s equaling less than one complete complement. Most terminate spont. Due to meiotic or mitotic ndj errors. Only viable one is 45,X
Mosaicism.
2 cell lines, one difference betw them caused by a translo mutation or mitotic ndj. Chimeras have multiple diff’s betw the cell lines.
Mosaicism can be caused by mitotic ndj resulting in a disomic and a trisomic cells by two means. Describe.
2N zygote, gain of trisomy. Trisomic zygote, loss of trisomy.
Most trisomies result in spont fetal loss. 3 can be live born. Which 3.
13,18,21.
Sex chromosome aneuploidies are all the result of what in when? List them.
NDJ errors in meiosis. Klinefelter syn 47,XXY; XYY male, XXX female, Turner syn 45,X.
XXX female facts
Usually due to maternal meiosis I error, avg to tall stature, may be infertile, learning deficits possible.
XYY Male facts
Failure of PATERNAL meiosis. Tall stature, nl intelligence and fertile.
Klinefelter syndrome 47,XXY facts
Males tall, thin, long legs. May have learning deficits. Post-pubertal hypogonadism, gynecomastia, infertility, small balls.
Turner facts
Most infertile, but with X/XX mosaicism might not be; also, donor egg technology can work. Having 2X’s early on in female devel is important, namely the short arms. Phenotypes highly variable include short stature, shield chest, neck webbing, low post hairline, cubitus valgus, no menses, heart and renal anomalies.
Turner causes and more facts
The single X chrom is usually from mom, thus a paternal meiotic ndj error. 15% have dels or rearr’s of the X, 10% are mosaics. Possessing a partial or complete Y increases risk of gonadoblastoma if female, ok if male.
Another situation resulting in an XY female is what, also known as “testicular feminization”. What’s intact on the Y and functional, but nonetheless what is still accounting for this person being a girl?
Androgen insensitivity. TDF intact, BUT there’s a mutation of the androgen receptor gene on the long arm of the X CHROMOSOME that results in no receptor made. TDF protein initiates male devel (inhib/degen Mull ducts), but without the androgen receptor no the cpx of DHT and testo can’t occur and no further male diffn is possible. Infertile. Blind vagina and testes in the abd.
How’s it possible to have an XX “Male”?
Virulizaton of female fetus via CAH (in mom or fetus), a defect resulting in lack of 21-hydroxylase. Normal ovaries and internal genitalia, ambiguous externally.