Question 1

Which DNA repair mechanism is primarily responsible for correcting UV-induced thymine dimers in human cells?

Accepted Answer

Nucleotide excision repair (NER)

Question 2

A patient with xeroderma pigmentosum has mutations in genes XPA-XPG. What process is defective in these individuals?

Accepted Answer

Nucleotide excision repair

Question 3

During DNA replication in E. coli, which enzyme is responsible for proofreading and removing incorrect nucleotides?

Accepted Answer

DNA polymerase III

Question 4

Which step occurs first in the mismatch repair pathway after a replication error is detected?

Accepted Answer

Endonuclease creates a nick near the mismatch

Question 5

Double-stranded breaks (DSBs) in DNA can lead to which of the following outcomes if not properly repaired?

Accepted Answer

Chromosomal rearrangements and cell death

Question 6

Which repair pathway uses a homologous region from a sister chromatid to accurately repair double-stranded breaks?

Accepted Answer

Homologous recombination (HR)

Question 7

What is the main function of short tandem repeats (STRs) in non-coding regions of the genome?

Accepted Answer

They regulate gene expression by affecting regulatory proteins

Question 8

The 'Onion Test' is used to challenge which assumption about the genome?

Accepted Answer

Genome size correlates with organism complexity

Question 9

According to ENCODE project findings, approximately what percentage of the human genome is estimated to have some function?

Accepted Answer

80%

Question 10

Which of the following is NOT considered a non-coding region of the genome?

Accepted Answer

Exons

Question 11

A mutation in the operator region of the lac operon would most likely affect which process?

Accepted Answer

Transcriptional regulation of structural genes

Question 12

Which experiment would best test the function of a suspected regulatory non-coding DNA element?

Accepted Answer

Knockout of the element followed by RNAseq analysis

Question 13

If a DNA lesion is skipped during replication, which protein directs the recombinational exchange to fill the gap?

Accepted Answer

RecA

Question 14

Which formula represents the probability $$P of a $$mutation occurring at a specific nucleotide site after $$n$$ rounds of replication, given a per-round error rate $$e$$?

Accepted Answer

$$P = 1 - (1 - e)^n$$

Question 15

Which of the following statements best describes the current understanding of 'junk DNA'?

Accepted Answer

A significant portion of non-coding DNA is involved in regulation and other functions

Question 16

In mismatch repair, which strand is targeted for correction?

Accepted Answer

The newly synthesized strand

Question 17

Which repair mechanism is most likely to introduce mutations during the repair of double-stranded breaks?

Accepted Answer

Non-homologous end joining (NHEJ)

Question 18

Which of the following is a plausible reason for the presence of large amounts of non-coding DNA in the human genome?

Accepted Answer

It provides regulatory elements and buffers against mutations

Question 19

Which process is responsible for sealing the final gap after DNA repair synthesis?

Accepted Answer

DNA ligase

Question 20

Which of the following best explains why genome size does not always correlate with organism complexity?

Accepted Answer

Non-coding DNA can vary greatly between species

DNA Repair Mechanisms, Non-Coding DNA, and Gene Expression (Lac Operon): Nov 3

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