Question 1

Which of the following statements best describes the mechanism by which DNA transposons (Class A) move within the genome?

Accepted Answer

They are excised from their original location by transposase and inserted into a new site, often leaving behind direct repeats at the insertion site.

Question 2

Barbara McClintock’s discovery of transposable elements in maize was based on which key observation?

Accepted Answer

Kernels and leaves showed variegated patterns that appeared and disappeared rapidly, not following classical Mendelian genetics.

Question 3

Which of the following is a feature unique to retrotransposons (Class B) compared to DNA transposons?

Accepted Answer

They transpose via an RNA intermediate and require reverse transcriptase for integration.

Question 4

A maize kernel shows large sectors of a recessive phenotype on a background of dominant phenotype. What does this indicate about the timing of the transposition event?

Accepted Answer

The transposition occurred early in kernel development, when there were few cells.

Question 5

Which of the following best explains how transposons can lead to gene duplication or deletion during meiosis?

Accepted Answer

Misalignment of homologous chromosomes due to transposons flanking a gene can result in unequal crossing-over, leading to duplication or deletion.

Question 6

Which of the following is NOT a typical genetic effect of transposon activity?

Accepted Answer

Facilitating the correct translation of a protein by adding essential amino acids.

Question 7

Which of the following human diseases has been associated with de novo insertions of retrotransposons?

Accepted Answer

Hemophilia due to Alu SINE insertion in the factor VIII gene

Question 8

What is the main difference between LINEs and SINEs in the human genome?

Accepted Answer

LINEs are autonomous and encode their own reverse transcriptase, while SINEs are non-autonomous and rely on LINEs' reverse transcriptase.

Question 9

Which of the following best describes the 'cut-and-paste' mechanism of DNA transposons?

Accepted Answer

A transposon is excised from its original site and inserted into a new site, leaving behind direct repeats at the insertion site.

Question 10

Which of the following statements about the composition of the human genome is correct?

Accepted Answer

Introns and transposable elements together constitute a significant portion of the genome, with protein-coding genes representing only a small fraction.

Question 11

A researcher finds a DNA sequence in the human genome with terminal inverted repeats and a gene encoding transposase, but no evidence of an RNA intermediate. This element is most likely:

Accepted Answer

A DNA transposon (Class A)

Question 12

Which of the following is a plausible consequence if a transposon inserts into the coding region of a gene?

Accepted Answer

The gene's protein product may be truncated or nonfunctional.

Question 13

Which of the following best explains why most human mariner elements are inactive?

Accepted Answer

They have accumulated mutations in the transposase gene, rendering them unable to transpose.

Question 14

Which of the following is a key feature of LTR retrotransposons in the human genome?

Accepted Answer

They have long terminal repeats (LTRs) with promoters, encode reverse transcriptase and integrase, but lack envelope proteins.

Question 15

A student claims that all transposons increase their copy number in the genome. Which of the following best addresses this misconception?

Accepted Answer

Only retrotransposons always increase their copy number; DNA transposons using the cut-and-paste mechanism do not.

Question 16

Which of the following best describes the role of direct repeats (DRs) in transposon insertion?

Accepted Answer

They are created at the target site during insertion and flank the inserted transposon.

Question 17

Which of the following is a real-world application of engineered transposons in biotechnology?

Accepted Answer

They are used as vectors for gene therapy and mutagenesis, such as the 'Sleeping Beauty' transposon system.

Question 18

Which of the following best explains why the human genome is still considered genetically unstable?

Accepted Answer

Active retrotransposons, such as LINEs and SINEs, continue to transpose and create new insertions.

Question 19

Which of the following is a plausible outcome if a transposon is excised from a gene, leaving behind its direct repeats?

Accepted Answer

The direct repeats may disrupt translation or protein function, potentially leading to a nonfunctional protein.

Transposable Genetic Elements and Genome Complexity: Study Notes for Biochemistry Students

Guida di studio - Domande di pratica

Study guide - Flashcard