Abnormalities of Chromosome Number

Question 1

Error in cell division whereby improper segregation leads to abnormal chromosome number (monosomy or trisomy)

Answer 1

Nondisjunction

Question 2

Presence of two cell lines in a person

Answer 2

Mosaicism

Question 3

Normal chromosome number

Answer 3

Euploidy

Question 4

Chromosome number that is not a multiple of 23

Answer 4

Aneuploidy

Question 5

Chromosome number that is a multiple of 23 (extra sets of chromosomes)

Answer 5

Polyploidy

Question 6

Caused by fertilization by two sperm

Answer 6

Triploidy

Question 7

Caused by failure of cell division

Answer 7

Tetraploidy

Question 8

All monosomies are lethal. Most trisomies are lethal except for which chromosomes?

Answer 8

13, 18, 21

Question 9

Sex chromosome aneuploidy is better tolerated than autosomal aneuploidy. What is the one necessity, however, for survival despite germ line aneuploidy?

Answer 9

Karyotype requires at least one X chromosome for survival

Question 10

What percentage of recognized pregnancies end in miscarriage?

Answer 10

15%

Question 11

What percentage of fertilized eggs do not come to term?

Answer 11

50%

Question 12

Leading cause of spontaneous abortions?

Answer 12

chromosome abnormalities

Question 13

Most common chromosomal disorder?

Answer 13

Trisomy 21 (Down’s)

Question 14

Etiology of Trisomy 21?

Answer 14

95% nondisjunction (especially maternal meiosis I) 5% Robertsonian translocation

Question 15

Rocker feet, clinched hands

Answer 15

Trisomy 18 (Edward’s syndrome)

Question 16

Etiology of Trisomy 18?

Answer 16

Maternal nondisjunction

Question 17

Midline deformations?

Answer 17

Trisomy 13 (Patau syndrome)

Question 18

Etiology of trisomy 13?

Answer 18

80% maternal nondisjunction

20% Robertsonian translocation

Question 19

Short stature, infertility, webbing of neck, normal intelligence

Answer 19

Turner syndrome (45,X)