Question 1

Which of the following best describes the flow of genetic information in most cells, and what is the exception to this rule?

Accepted Answer

DNA → RNA → protein; exception is reverse transcription where RNA is used to make DNA

Question 2

During transcription, which enzyme is responsible for synthesizing RNA from a DNA template, and what is the correct base pairing?

Accepted Answer

RNA polymerase; $$A$$ pairs with $$U$$, $$G$$ pairs with $$C$$

Question 3

Which process allows some viruses to synthesize DNA from an RNA template, and what enzyme is required?

Accepted Answer

Reverse transcription; requires reverse transcriptase

Question 4

In eukaryotic cells, what is the purpose of mRNA splicing, and which molecular complex is responsible for this process?

Accepted Answer

To remove introns and join exons, increasing protein diversity; spliceosome

Question 5

Which statement correctly distinguishes between prokaryotic and eukaryotic mRNA?

Accepted Answer

Prokaryotic mRNA is often polycistronic, while eukaryotic mRNA is usually monocistronic

Question 6

Which of the following is NOT a function of ribosomal RNA (rRNA)?

Accepted Answer

Carrying amino acids to the ribosome

Question 7

How many unique codons are possible in the genetic code, and how many of these encode amino acids?

Accepted Answer

$$64$$ unique codons; $$61$$ encode amino acids

Question 8

What is the significance of redundancy in the genetic code?

Accepted Answer

It allows multiple codons to code for the same amino acid, protecting against some mutations

Question 9

Which step of translation involves the ribosome moving along the mRNA and adding amino acids to the growing polypeptide chain?

Accepted Answer

Elongation

Question 10

A mutation changes the codon $$UAC ($$tyrosine) to $$UAA in an $$mRNA sequence. What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; results in premature termination of translation

Question 11

Which of the following best explains why base substitution mutations are generally less disruptive than insertion or deletion mutations?

Accepted Answer

Base substitutions may only change one amino acid, while insertions/deletions can cause frameshifts affecting all downstream amino acids

Question 12

Which enzyme is responsible for repairing DNA by removing damaged bases and filling in the gap, and what is this process called?

Accepted Answer

Excision repair; DNA polymerase

Question 13

A scientist exposes bacteria to a chemical and observes a significant increase in colonies on a medium lacking histidine. What does this result suggest about the chemical?

Accepted Answer

It is a mutagen that induces mutations allowing histidine synthesis

Question 14

Which type of horizontal gene transfer involves the uptake of naked DNA from the environment by competent cells?

Accepted Answer

Transformation

Question 15

What is the role of the F plasmid in bacterial conjugation?

Accepted Answer

It encodes the ability to form a pilus for DNA transfer between cells

Question 16

Which of the following is a post-translational modification that can affect protein function?

Accepted Answer

Addition of phosphate groups (phosphorylation)

Question 17

A frameshift mutation occurs when:

Accepted Answer

Nucleotides are inserted or deleted, altering the reading frame of the gene

Question 18

Which class of RNA contains an anticodon loop and is responsible for delivering amino acids to the ribosome?

Accepted Answer

Transfer RNA (tRNA)

Question 19

Why is regulation of protein synthesis at the pre-transcriptional level considered more energy efficient than post-transcriptional regulation?

Accepted Answer

It prevents unnecessary synthesis of RNA and proteins, conserving cellular resources

Chap 5B

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