MCM 2-30 Cytogenics Introduction

Question 1

Fetal Loss Statistics

___ of recognize fertilizations fail

____ in first trimester

___ due to chromosome abnormalities

_____ of chromosomal losses are autosomal trisomies

Answer 1

most fertilizations fail
15% of recognized fertilizations fail
80% in first trimester

60% due to chromosome abnormalities

52% are autosomal trisomies

Question 2

triploidy has how many chromosomes?

Answer 2

69, 3 of each

Question 3

ploidy =

euploid =
diploid =
triploid =
tetraploid =

Answer 3

how many sets of chromosomes we have

euploid - 1 set (1n)
diploid (2n)
triploid (3n)
tetraploid (4n)

Question 4

aneuploid?

Answer 4

not a full multiple of 23

ex) monosomy, only 1
or trisomy (3 instead of 2)

Question 5

when can nondisjunction occur?

Answer 5

in first cell division

Question 6

Meiotic nondisjunction; anaphase I nondisjunction can lead to

Answer 6

two disomic/ n+1 games, two monosomic/ n-1 gametes

which can lead to

trisomy and monoloid zygotes

Question 7

nondisjunction in meiosis 2 will lead to

Answer 7

2 normal, 1 disomic (n+1) and 1 nullsomic (n-1)

Question 8

correct way to write a female with extra chromosome 13?

male missing a chromosome 8?

Answer 8

47,XX,+13

45,XY,-8

Question 9

aneuploidy can be caused by nondisjunction in

Answer 9

mitosis or meiosis

Question 10

Mosaicism

examples?

how is it inherited?

Answer 10

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

Question 11

viable autosomal trisomies and features of each

Answer 11

Downs syndrome - trisomy 21

Patau Syndrome - Trisomy 13 (cleft lip and palate)

Edwards Syndrome - trisomy 18. Worst prognosis, rocker feet

Question 12

Sex chromosome Aneuploidies (4)

Answer 12

Klinefelter Syndrome - 47,XXY

XYY male

XXX female

turner Syndrome: 45,X

Question 13

sex determination is based on..

Answer 13

genes on X, Y, and autosome chromosomes

Question 14

TDF/SRY

Answer 14

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

Question 15

appearance of XX female somatic cells? XXX?

Answer 15

XX female will have a single bar body in her cells

XXX femlaes will have two barr bodies

Question 16

X inactivation is random but

Answer 16

once established, is not reversible in SOMATIC tissues

Question 17

females are mosaics for..

Answer 17

heterozygous traits

Question 18

what causes Aneuploidy?

ex?

Answer 18

gain or loss of a chromosomes equaling less than one complete complement

ex) trisomy and monosomy