Question 1

Which of the following best describes a transposable element?

Accepted Answer

A sequence of DNA that can move to different positions within the genome of a single cell.

Question 2

Barbara McClintock’s work with corn led to the discovery of which genetic phenomenon?

Accepted Answer

Transposition of mobile genetic elements

Question 3

A DNA transposable element typically encodes which enzyme necessary for its movement?

Accepted Answer

Transposase

Question 4

Which of the following is a consequence of a transposable element inserting into an open reading frame of a gene?

Accepted Answer

Disruption of gene function, potentially causing a mutant phenotype

Question 5

Which of the following best explains why almost half of the human genome consists of ancient transposable elements and viruses?

Accepted Answer

Cells lack a repair mechanism to remove transposable element insertions, allowing them to accumulate over evolutionary time.

Question 6

Which chromosomal abnormality is responsible for Cri-du-chat syndrome?

Accepted Answer

A terminal deletion in the short arm of chromosome 5

Question 7

What is the most common viable autosomal trisomy in humans?

Accepted Answer

Trisomy 21 (Down syndrome)

Question 8

Which of the following best describes the mechanism of dosage compensation in placental mammals?

Accepted Answer

One X chromosome is randomly inactivated in each female somatic cell.

Question 9

A female mammal heterozygous for an X-linked gene is described as a genetic mosaic. What is the molecular basis for this phenomenon?

Accepted Answer

Random X chromosome inactivation in different cells

Question 10

Which of the following chromosomal abnormalities is most likely to result in the formation of a fusion gene that contributes to cancer, such as the Philadelphia chromosome?

Accepted Answer

Reciprocal translocation

Question 11

Which of the following is a likely outcome if nondisjunction occurs during meiosis I?

Accepted Answer

All resulting gametes will have an abnormal chromosome number.

Question 12

Which of the following best describes a pericentric inversion?

Accepted Answer

A chromosomal inversion that includes the centromere

Question 13

Which of the following is a plausible evolutionary advantage of chromosomal duplications?

Accepted Answer

They provide extra gene copies, allowing one to evolve a new function while the other maintains the original function.

Question 14

A plant species is found to have 69 chromosomes per cell. Which term best describes its chromosome number?

Accepted Answer

Triploid ($$3N)$$

Question 15

Which of the following is NOT a mechanism by which a transposable element can move within a genome?

Accepted Answer

Triplet expansion

Question 16

Which of the following best explains why females with three X chromosomes (47, XXX) are usually phenotypically normal?

Accepted Answer

X inactivation results in only one active X chromosome in each cell.

Question 17

Which of the following is a common feature of insertion sequences (IS elements) in bacteria?

Accepted Answer

They have terminal inverted repeats and carry a gene for transposase.

Question 18

A patient is diagnosed with Klinefelter syndrome. What is the chromosomal composition of this individual?

Accepted Answer

$$47,\ XXY$$

Question 19

Which of the following is a likely result of a duplication event that moves a gene next to a new regulatory region?

Accepted Answer

Abnormal gene expression and potentially novel phenotypes

Question 20

Which of the following best describes an aneuploid cell?

Accepted Answer

A cell with an incorrect number of chromosomes

Transposable Elements and Chromosomal Abnormalities: Genetics Study Notes

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