Chromosomal Abnormalities

Question 1

Turner’s Syndrome

Answer 1

Monosomy X chromosome

Question 2

Down Syndrome

Answer 2

trisomy 21; MR, palmar crease, decreased tone, heart defects, facial appearance

Question 3

Trisomy 21 cause

Answer 3

nondisjunction during maternal gametogenesis (complete trisomy)

Question 4

Causes of Triploidy

Answer 4

2 sperm fertilize 1 egg (60%), fertilization of diploid egg by 1 sperm (20%), and fertilization of 1 egg by diploid sperm (5%)

Question 5

Causes of Tetraploidy

Answer 5

chromosomes duplicate but segregate only to 1 daughter cell

Question 6

Molecular Basis of Down Syndrome

Answer 6

Overexpression of a Down Syndrome critical region - SOD1, COL6A1, ETS2, DYRK, APP

Question 7

SOD1

Answer 7

overexpression causes accumulation of H2O2

Question 8

COL6A1

Answer 8

overexpression may cause heart defects

Question 9

ETS2

Answer 9

overexpression may cause hypotonia

Question 10

DYRK

Answer 10

overexpression may cause mental retardation

Question 11

APP

Answer 11

overexpression may cause early Alzheimer’s

Question 12

Causes of Down Syndrome

Answer 12

1. Nondisjunction of maternal gamete (95%)
2. Robertsonian Translocation (4%)
3. Mosaicism (1-2%)

Question 13

Robertsonian Translocation

Answer 13

Short arm of 14 replaced with long arm of 21, creating a hybrid chromosome; gamete with (21 + t21:14) results in Down Syndrome following fertilization

Question 14

Mosaicism

Answer 14

46-47 chromosomes, variable presentation
Somatic origin: mitotic nondisjunction of fertilized egg
Meiotic origin: 47 chromosomes in egg; Anaphase lag rescues the trisomy in some mitotically dividing cells, resulting in some cells with 46, some with 47

Question 15

Patau Syndrome

Answer 15

Trisomy 13 - low survival rate; small head, cleft lip, clenched hands, poldacytly

Question 16

Edwards Syndrome

Answer 16

Trisomy 18 - low survival; prominent occiput, dysplastic ear, clenched hand, small jaw

Question 17

Klinefelter’s XXY

Answer 17

trisomy XXY; less muscular body, less facial and body hair, and broader hips. As teens, XXY males may have larger breasts, weaker bones, and a lower energy level than other boys; characterized by nondisjunction of gametes during meiosis I

Question 18

Turners X

Answer 18

monosomy X; short stature, swelling, broad chest, low hairline, low-set ears, and webbed necks; mosaicism with deleted X chromosome

Question 19

Trisomy X

Answer 19

XXX

Question 20

XYY Syndrome

Answer 20

XYY

Question 21

Example of reciprocal translocation

Answer 21

Burkitt’s Lymphoma (c-myc), chronic myelogenous leukemia (BCR-ABL)

Question 22

Example of Robertsonian translocation

Answer 22

Down Syndrome

Question 23

Inversions

Answer 23

two DSBs and genetic material reinserted flipped around

Question 24

Angelmans and Prader-Wili)

Answer 24

microdeletion

Question 25

Example of Deletions

Answer 25

Cri-du-Chat Syndrome, Wolf-Hirschhorn

Question 26

Examples of duplication loci

Answer 26

x-linked color visions loci