Numerical and Structural Chromosomal Abnormalities - IN Flashcards
make it rain on dem hoez (23 cards)
Define Euploidy
Exact multiples of haploid set of chromosomes (N, 2N, 3N, 4N…)
Define Triploidy
failure in gametogenesis so you end with a 2N gamete, which results in a 3N zygote
When does Tetraploidy occur
post meiotic event, usually a failure in early mitotic division within the zygote (XXXX or XXYY)
Define Aneuploidy
gain or loss of an individual chromosome
Define Mosaicism
presence of at least 2 different cell lines with at least one clear variation between them (2 flavors) - ALSO mosaics are acquired, not inherited
Are any trisomies viable?
Yes, Down T21; Patau T13; Edwards T18
Talk to me about XYY
male, exclusively paternal, tall but pretty much normal, clinically indistinguishable from 46, XY
Talk to me about XXX
female, usually maternal meiosis I error, learning deficits and fertility issues, often undetected through life
Whats a Klinefelter?
47, XXY - male, tall and thin, long legs and fingers, infertility, testicular dysgenesis, man boobies develop
Whats a Turner?
45, X - female, short, webbed neck, short hands and fingers, shield chest, usually infertile
What causes an XY Female
androgen insensitivity - mutation of androgen receptor located on long arm of X chrom.
What causes an XX Male
whatever is in the water in bartlow’s hometown
What causes an XX Male (actually though)
Congenital Adrenal Hyperplasia, lack of 21-a-hydroxylase results in overproduction of androgens, causes normal internal genitalia but ambiguous external genitalia
What is a balanced abnormality?
all material is present, just rearranged, usually clinically benign
what is an unbalanced abnormality?
some material is missing
Define Deletion
loss of part of a chromosome, leading to a partial monosomy
what is the difference between a terminal and interstitial deletion
terminal - one break only, at distal end (e.g. Wolf-Hirschhorn)
interstitial - requires 2 breaks, internally
Define Duplication
additional copy of chromosome segment, results in partial trisomy
Define Translocation
equal, reciprocal exchange between two or more chromosomes
What is a Robertsonian Translocation
occur only between 2 acrocentric centromeres and appear as a fusion of long arms at the centromere
Define Inversion
reversal of a chromosomal segment with respect to the normal gene arrangement, requires a minimum of two breaks in the chromosome
(larger inversion, smaller errors; smaller inversion, larger errors)
Define pericentric
breaks occur on opposite sides of the centromere
define paracentric
breaks occur on same side of centromere, on same arm, usually clinically benign
