Question 1

Which of the following best describes a transposable element?

Accepted Answer

A segment 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 transposon 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

In Mendel’s pea plants, the wrinkled seed phenotype is caused by:

Accepted Answer

Insertion of a transposable element that disrupts gene function.

Question 6

Which of the following best explains why Down syndrome (trisomy 21) is viable while most other autosomal trisomies are not?

Accepted Answer

Chromosome 21 is the smallest human chromosome, so having an extra copy is less disruptive.

Question 7

A patient is diagnosed with Cri-du-chat syndrome. Which chromosomal abnormality is responsible for this condition?

Accepted Answer

Terminal deletion on the short arm of chromosome 5.

Question 8

Which of the following mechanisms leads to aneuploidy during meiosis?

Accepted Answer

Nondisjunction of homologous chromosomes or sister chromatids.

Question 9

Which of the following is true about X-chromosome inactivation in female mammals?

Accepted Answer

One X chromosome is randomly inactivated in each somatic cell, resulting in dosage compensation.

Question 10

A calico cat’s fur pattern is a classic example of which genetic phenomenon?

Accepted Answer

Genetic mosaicism due to X-chromosome inactivation.

Question 11

Which of the following best describes a reciprocal translocation?

Accepted Answer

Two chromosomes exchange segments with each other.

Question 12

What is the result of a 'cut and paste' transposition mechanism?

Accepted Answer

The transposable element is excised from its original site and inserted into a new site.

Question 13

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

Accepted Answer

Reciprocal translocation between chromosomes 9 and 22.

Question 14

A human cell with 69 chromosomes is best described as:

Accepted Answer

Triploid ($$3N)$$

Question 15

Which of the following is a possible 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 16

Which of the following statements about retrotransposons is correct?

Accepted Answer

They transpose through an RNA intermediate.

Question 17

A woman with a 47, XXX karyotype is most likely to:

Accepted Answer

Be phenotypically normal due to X inactivation.

Question 18

Which of the following best explains why transposable element insertions tend to accumulate in genomes over evolutionary time?

Accepted Answer

Cells lack a repair mechanism to remove transposable element insertions.

Question 19

Which of the following is NOT a structural chromosomal abnormality?

Accepted Answer

Aneuploidy

Question 20

If nondisjunction occurs during meiosis II, what is the expected outcome for the resulting gametes?

Accepted Answer

Two normal gametes, one gamete with an extra chromosome, and one gamete missing a chromosome.

Transposable Elements and Chromosomal Abnormalities: Genetics Study Notes

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