Numerical and Structural Chromosomal Abnormalities - IN

Question 1

Define Euploidy

Answer 1

Exact multiples of haploid set of chromosomes (N, 2N, 3N, 4N…)

Question 2

Define Triploidy

Answer 2

failure in gametogenesis so you end with a 2N gamete, which results in a 3N zygote

Question 3

When does Tetraploidy occur

Answer 3

post meiotic event, usually a failure in early mitotic division within the zygote (XXXX or XXYY)

Question 4

Define Aneuploidy

Answer 4

gain or loss of an individual chromosome

Question 5

Define Mosaicism

Answer 5

presence of at least 2 different cell lines with at least one clear variation between them (2 flavors) - ALSO mosaics are acquired, not inherited

Question 6

Are any trisomies viable?

Answer 6

Yes, Down T21; Patau T13; Edwards T18

Question 7

Talk to me about XYY

Answer 7

male, exclusively paternal, tall but pretty much normal, clinically indistinguishable from 46, XY

Question 8

Talk to me about XXX

Answer 8

female, usually maternal meiosis I error, learning deficits and fertility issues, often undetected through life

Question 9

Whats a Klinefelter?

Answer 9

47, XXY - male, tall and thin, long legs and fingers, infertility, testicular dysgenesis, man boobies develop

Question 10

Whats a Turner?

Answer 10

45, X - female, short, webbed neck, short hands and fingers, shield chest, usually infertile

Question 11

What causes an XY Female

Answer 11

androgen insensitivity - mutation of androgen receptor located on long arm of X chrom.

Question 12

What causes an XX Male

Answer 12

whatever is in the water in bartlow’s hometown

Question 13

What causes an XX Male (actually though)

Answer 13

Congenital Adrenal Hyperplasia, lack of 21-a-hydroxylase results in overproduction of androgens, causes normal internal genitalia but ambiguous external genitalia

Question 14

What is a balanced abnormality?

Answer 14

all material is present, just rearranged, usually clinically benign

Question 15

what is an unbalanced abnormality?

Answer 15

some material is missing

Question 16

Define Deletion

Answer 16

loss of part of a chromosome, leading to a partial monosomy

Question 17

what is the difference between a terminal and interstitial deletion

Answer 17

terminal - one break only, at distal end (e.g. Wolf-Hirschhorn)
interstitial - requires 2 breaks, internally

Question 18

Define Duplication

Answer 18

additional copy of chromosome segment, results in partial trisomy

Question 19

Define Translocation

Answer 19

equal, reciprocal exchange between two or more chromosomes

Question 20

What is a Robertsonian Translocation

Answer 20

occur only between 2 acrocentric centromeres and appear as a fusion of long arms at the centromere

Question 21

Define Inversion

Answer 21

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)

Question 22

Define pericentric

Answer 22

breaks occur on opposite sides of the centromere

Question 23

define paracentric

Answer 23

breaks occur on same side of centromere, on same arm, usually clinically benign