Question 1

Which of the following best describes a pericentric inversion?

Accepted Answer

A chromosomal segment is inverted and the inversion includes the centromere.

Question 2

A child is diagnosed with cri-du-chat syndrome. Which chromosomal abnormality is most likely responsible for this condition?

Accepted Answer

A deletion on the short arm (p arm) of chromosome 5.

Question 3

Which of the following mechanisms can lead to copy number variation (CNV) in the human genome?

Accepted Answer

Nonallelic homologous recombination, proliferation of transposable elements, and errors in DNA replication.

Question 4

A chromosome undergoes two breaks and the central fragment is lost. The two outer pieces rejoin. What is this type of chromosomal mutation called?

Accepted Answer

Interstitial deletion

Question 5

Which of the following statements about gene families is correct?

Accepted Answer

Gene families arise through gene duplication events followed by the accumulation of mutations in the duplicated genes.

Question 6

In an inversion heterozygote, what is the most likely outcome if crossing over occurs within the inversion loop during meiosis I?

Accepted Answer

Gametes with duplications and deletions, leading to a high probability of inviable offspring.

Question 7

Which of the following best explains why duplications are important for evolution?

Accepted Answer

Duplications provide extra genetic material that can evolve new functions, leading to gene families.

Question 8

A person is a carrier of a Robertsonian translocation involving chromosomes 14 and 21. If this person produces gametes, what is the probability that a gamete will have a balanced set of chromosomes (either normal or balanced carrier)?

Accepted Answer

$$\frac{2}{6} (or 1/3)$$

Question 9

Which meiotic segregation pattern in a reciprocal translocation carrier produces only genetically balanced gametes?

Accepted Answer

Alternate segregation

Question 10

A chromosome segment is transferred from one chromosome to a non-homologous chromosome, with no reciprocal exchange. What is this event called?

Accepted Answer

Simple translocation

Question 11

Which of the following is a likely consequence of adjacent-1 segregation in a reciprocal translocation heterozygote?

Accepted Answer

All gametes are genetically unbalanced, often leading to semisterility.

Question 12

Which of the following best describes the difference between a paracentric and a pericentric inversion?

Accepted Answer

A paracentric inversion does not include the centromere, while a pericentric inversion does.

Question 13

Which of the following is NOT a possible outcome of crossing over within a paracentric inversion loop during meiosis?

Accepted Answer

A chromosome with increased fertility

Question 14

Which of the following is true regarding the phenotypic consequences of deletions?

Accepted Answer

The severity depends on both the size of the deletion and the specific genes lost.

Question 15

Which of the following is a real-world example of a gene family formed by duplication and divergence?

Accepted Answer

The globin gene family, which includes myoglobin and hemoglobin genes.

Question 16

If a segment of DNA is present in three copies in one individual and only one copy in another individual of the same species, this is an example of:

Accepted Answer

Copy number variation (CNV)

Question 17

Which of the following equations correctly represents the proportion of the human genome that typically shows copy number variation?

Accepted Answer

$$0.004 = 0.4\%$$

Question 18

Which of the following is a possible outcome for the offspring of a carrier of a Robertsonian translocation between chromosomes 14 and 21, after fertilization with a normal gamete?

Accepted Answer

Familial Down Syndrome, due to three copies of the long arm of chromosome 21.

Question 19

Which of the following best explains why individuals with reciprocal translocations often exhibit semisterility?

Accepted Answer

They produce a high proportion of unbalanced gametes due to adjacent-1 segregation.

Question 20

Which of the following is a plausible mechanism by which a gene may acquire a new regulatory environment, potentially altering its expression pattern?

Accepted Answer

A position effect caused by an inversion that relocates the gene next to different regulatory elements.

Variation in Chromosome Structure and Number

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