Question 1

Which of the following best describes a terminal deletion in a chromosome?

Accepted Answer

A segment at the end of the chromosome is lost due to a single break, and the acentric fragment is degraded.

Question 2

A patient is diagnosed with WAGR syndrome, which is caused by a deletion on chromosome 11. Which type of chromosomal structural change is most likely responsible?

Accepted Answer

Interstitial deletion

Question 3

Which chromosomal abnormality is described by the formula $$2N-2$$?

Accepted Answer

Nullisomy

Question 4

In a reciprocal balanced translocation, what is the outcome for gametes after alternate segregation during meiosis?

Accepted Answer

Gametes contain a full haploid set of genes and are viable.

Question 5

Which of the following best describes a paracentric inversion?

Accepted Answer

The centromere is outside the inverted region.

Question 6

A chromosome undergoes two breaks and the segment between them is rotated 180 degrees before rejoining. If the centromere is included in the inverted segment, what is this called?

Accepted Answer

Pericentric inversion

Question 7

Which chromosomal mutation results in the doubling of a segment of a chromosome, with the duplicated segment adjacent to the original in the same order?

Accepted Answer

Tandem duplication

Question 8

What is the most likely outcome when crossing over occurs within the inversion loop of a paracentric inversion heterozygote?

Accepted Answer

Formation of a dicentric chromosome and an acentric fragment, both missing genetic material.

Question 9

Which chromosomal mutation is most likely to result in semi-sterility due to abnormal segregation during meiosis?

Accepted Answer

Reciprocal balanced translocation

Question 10

A carrier of a Robertsonian translocation involving chromosomes 14 and 21 is phenotypically normal. What is the risk for their offspring?

Accepted Answer

Increased risk of Down syndrome due to trisomy 21.

Question 11

Which of the following best describes an unbalanced translocation?

Accepted Answer

A one-way transfer of a segment from one chromosome to a nonhomologous chromosome, resulting in gene dosage imbalance.

Question 12

What is the chromosomal composition of a tetrasomic individual?

Accepted Answer

$$2N+2$$

Question 13

Which technique is most useful for detecting microdeletions and microduplications that are too small to be seen microscopically?

Accepted Answer

Fluorescent in situ hybridization (FISH)

Question 14

Which chromosomal abnormality is most likely to result from unequal crossover between homologous chromosomes?

Accepted Answer

Partial duplication on one homolog and partial deletion on the other

Question 15

Which of the following is NOT a consequence of crossing over within the inversion loop in inversion heterozygotes?

Accepted Answer

Production of only normal gametes

Question 16

Which chromosomal mutation is most likely to cause cri-du-chat syndrome?

Accepted Answer

Terminal deletion of chromosome 5

Question 17

Which of the following best describes a pericentric inversion?

Accepted Answer

The centromere is within the inverted region.

Question 18

What is the result of a Robertsonian translocation in terms of chromosome number?

Accepted Answer

$$2N-2$$

Question 19

Which chromosomal mutation is most likely to result in gene dosage imbalance and severe abnormalities?

Accepted Answer

Loss or gain of chromosome segments (deletion or duplication)

Question 20

Which of the following is a real-world example of a syndrome caused by an interstitial deletion?

Accepted Answer

WAGR syndrome

Chromosomal Structural Variations: Deletions, Duplications, Inversions, and Translocations

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