Question 1

Which experiment provided the first direct evidence that DNA, and not protein, is the genetic material, and what was the key innovative technique used?

Accepted Answer

Avery, MacLeod, and McCarty’s experiment; they used enzymatic digestion to selectively destroy DNA, RNA, or protein.

Question 2

Which of the following best describes the Meselson and Stahl experiment and its conclusion about DNA replication?

Accepted Answer

They used density gradient centrifugation with $$^{15}N$$ and $$^{14}N$$ isotopes to demonstrate that DNA replication is semi-conservative.

Question 3

Which of the following statements about histone proteins and their post-translational modifications is correct?

Accepted Answer

Histone acetylation occurs mainly on lysine residues in the N-terminal tails and typically results in relaxed chromatin and increased gene expression.

Question 4

During DNA replication in prokaryotes, which enzyme is responsible for removing RNA primers and replacing them with DNA nucleotides?

Accepted Answer

DNA Polymerase I

Question 5

What is the main problem with replicating the ends of linear eukaryotic chromosomes, and how is it solved?

Accepted Answer

The lagging strand cannot be fully replicated at the ends, leading to telomere shortening; telomerase extends the telomeres using an RNA template.

Question 6

Which of the following best describes the Central Dogma of Molecular Biology and one of its exceptions?

Accepted Answer

DNA is transcribed to RNA, which is translated to protein; an exception is reverse transcription in retroviruses.

Question 7

Which feature of the genetic code allows for silent mutations, and how does it work?

Accepted Answer

The code is redundant, with variability often in the third position (wobble), so different codons can code for the same amino acid.

Question 8

Which of the following statements about mRNA processing in eukaryotes is correct?

Accepted Answer

The 3’ poly-A tail is added to increase mRNA stability and assist in export from the nucleus.

Question 9

A mutation in the gene encoding the nuclear localization signal (NLS) of a protein would most likely result in which of the following?

Accepted Answer

The protein would fail to enter the nucleus and remain in the cytoplasm.

Question 10

Which of the following best explains how alternative splicing can increase protein diversity in eukaryotic cells?

Accepted Answer

By allowing different combinations of exons to be included in the final mRNA, producing different proteins from the same gene.

Question 11

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

In eukaryotes, mRNA is processed and transported out of the nucleus before translation, while in prokaryotes, translation can begin before transcription is complete.

Question 12

Which of the following best describes the role of microRNA (miRNA) in gene regulation?

Accepted Answer

miRNA binds to mRNA and inhibits translation or promotes degradation.

Question 13

A cell is exposed to high levels of iron. How does this affect the translation of ferritin and transferrin receptor mRNAs?

Accepted Answer

Ferritin translation increases and transferrin receptor translation decreases due to changes in mRNA secondary structure.

Question 14

Which checkpoint in the cell cycle is primarily responsible for ensuring that all chromosomes are properly attached to the spindle before separation?

Accepted Answer

M (Metaphase/Anaphase) checkpoint

Question 15

What is the normal function of the tumor suppressor protein p53 in the cell cycle?

Accepted Answer

It repairs DNA damage or initiates apoptosis if the damage is irreparable.

Question 16

Which of the following best describes the difference between a polycistronic and a monocistronic mRNA?

Accepted Answer

Polycistronic mRNA encodes multiple proteins from a single mRNA, while monocistronic mRNA encodes only one protein.

Question 17

In the context of CRISPR-Cas9 gene editing, what is the role of the guide RNA (gRNA)?

Accepted Answer

It directs the Cas9 protein to a specific DNA sequence by base pairing.

Question 18

A patient has a mutation in the gene encoding a DNA repair enzyme. Which of the following outcomes is most likely?

Accepted Answer

Increased mutation rate and higher risk of cancer.

Question 19

Which of the following best explains why SARS and MERS outbreaks were more easily contained than COVID-19?

Accepted Answer

They were less transmissible before symptoms appeared, allowing for effective isolation.

Question 20

In Sanger (dideoxy) DNA sequencing, what is the effect of incorporating a dideoxynucleotide into a growing DNA strand?

Accepted Answer

It terminates DNA synthesis at that point because it lacks a 3’ hydroxyl group.

Comprehensive Study Guide: DNA, Gene Expression, Cell Cycle, and Biotechnology

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