Chromosome Variation and Structure

Question 1

Down’s Syndrome

Answer 1

Trisomy 21

Question 2

Cause of aneuploidy

Answer 2

Nondisjunction in mitosis, meiosis I, or meiosis II

Question 3

Nullisomy

Answer 3

Loss of both members of a homologous pair of chromosomes 2n - 2

Question 4

Monosomy

Answer 4

Loss of a single chromosome 2n - 1

Question 5

Trisomy

Answer 5

Gain of a single chromosome 2n + 1

Question 6

Tetrasomy

Answer 6

Gain of two homologous chromosomes 2n + 2

Question 7

Trisomy 18

Answer 7

Edward Syndrome 1/8,000 live births

Question 8

Trisomy 13

Answer 8

Patau Syndrome 1/15,000 live births

Question 9

Trisomy 8

Answer 9

1/25,000 - 1/50,000 live births

Question 10

Robertsonian translocation

Answer 10

The short arm of one acrocentric chromosome is exchanged with the long arm of another.

Question 11

Positive supercoiling

Answer 11

DNA is overrotated and the helix twists in on itself

Question 12

Negative supercoiling

Answer 12

DNA is underrotated and the helix twists in on itself in the opposite direction

Question 13

Nucleosome

Answer 13

DNA packaged around a histone

Question 14

Telomere

Answer 14

Prevent nucleases from chewing the ends of chromosomes

Question 15

Transposable element

Answer 15

DNA sequence that can move around in the genome, causing duplications, deletions and other rearrangements.