Flashcards in MCM 2-30 Cytogenics Introduction Deck (18)
Fetal Loss Statistics
___ of recognize fertilizations fail
____ in first trimester
___ due to chromosome abnormalities
_____ of chromosomal losses are autosomal trisomies
most fertilizations fail
15% of recognized fertilizations fail
80% in first trimester
60% due to chromosome abnormalities
52% are autosomal trisomies
triploidy has how many chromosomes?
69, 3 of each
how many sets of chromosomes we have
euploid - 1 set (1n)
not a full multiple of 23
ex) monosomy, only 1
or trisomy (3 instead of 2)
when can nondisjunction occur?
in first cell division
Meiotic nondisjunction; anaphase I nondisjunction can lead to
two disomic/ n+1 games, two monosomic/ n-1 gametes
which can lead to
trisomy and monoloid zygotes
nondisjunction in meiosis 2 will lead to
2 normal, 1 disomic (n+1) and 1 nullsomic (n-1)
correct way to write a female with extra chromosome 13?
male missing a chromosome 8?
aneuploidy can be caused by nondisjunction in
mitosis or meiosis
how is it inherited?
presence of at least 2 different cell lines with at least one clear variation between them
cell lines with numerical changes 45,X and 46,XX
cell lines with structural change - one cell line with translocation that doesnt occur in the other
mosiacism is not inherited, only acquired
viable autosomal trisomies and features of each
Downs syndrome - trisomy 21
Patau Syndrome - Trisomy 13 (cleft lip and palate)
Edwards Syndrome - trisomy 18. Worst prognosis, rocker feet
Sex chromosome Aneuploidies (4)
Klinefelter Syndrome - 47,XXY
turner Syndrome: 45,X
sex determination is based on..
genes on X, Y, and autosome chromosomes
SRY = sex determining region on the Y chromosome encodes testes determining factor
Females lack TDF/SRY - formation of ovary, proliferation of mullerian and regresson of wolffian ducts
males have TDF/SRY - formation of testes which inhibit/degrade mullerian ducts and product testosterone to proliferate wolffian ducts
appearance of XX female somatic cells? XXX?
XX female will have a single bar body in her cells
XXX femlaes will have two barr bodies
X inactivation is random but
once established, is not reversible in SOMATIC tissues
females are mosaics for..