Question 1

Which feature of the genetic code allows multiple codons to specify the same amino acid, and what is the significance of this feature?

Accepted Answer

Degeneracy; it reduces the impact of mutations by allowing silent changes.

Question 2

A mutation changes a codon from UGG to UGA in a gene. What is the most likely outcome for the protein product?

Accepted Answer

Translation will terminate prematurely, resulting in a truncated protein.

Question 3

Which codon serves as the universal start signal for translation in most organisms, and which amino acid does it encode?

Accepted Answer

AUG; methionine

Question 4

According to the wobble hypothesis, which position in the codon is most likely to tolerate non-standard base pairing?

Accepted Answer

Third position

Question 5

In human mitochondria, the codon UGA is interpreted differently than in the universal genetic code. What does UGA encode in human mitochondria?

Accepted Answer

Tryptophan

Question 6

Which of the following best describes the role of the σ (sigma) factor in bacterial transcription?

Accepted Answer

It recognizes and binds to promoter sequences to initiate transcription.

Question 7

What is the difference between cis-acting elements and trans-acting factors in gene regulation?

Accepted Answer

Cis-acting elements are adjacent DNA sequences; trans-acting factors are proteins that bind to these sequences.

Question 8

Which equation represents the number of possible codons given four different ribonucleotide bases and a triplet code?

Accepted Answer

$$4^3$$

Question 9

A frameshift mutation occurs when a single nucleotide is inserted into a coding sequence. What is the most likely effect on the resulting protein?

Accepted Answer

The reading frame will shift, altering all downstream amino acids.

Question 10

Which of the following statements about transcription in prokaryotes and eukaryotes is correct?

Accepted Answer

Prokaryotic transcription produces polycistronic mRNA, while eukaryotic transcription typically produces monocistronic mRNA.

Question 11

Which consensus sequence is commonly found in the −10 region of bacterial promoters and is essential for transcription initiation?

Accepted Answer

TATAAT

Question 12

During transcription, which strand of DNA is used as the template for RNA synthesis?

Accepted Answer

Template strand

Question 13

Which of the following is NOT a feature of the genetic code?

Accepted Answer

It is ambiguous.

Question 14

If a gene contains the sequence 5'-TACCAAACCG-3' on the template strand, what is the corresponding mRNA sequence?

Accepted Answer

5'-AUGGUUUGGC-3'

Question 15

Which of the following statements about RNA polymerase is true?

Accepted Answer

It uses ribonucleotide substrates to synthesize RNA.

Question 16

What is the function of termination codons during translation?

Accepted Answer

They are not recognized by tRNA and cause translation to stop.

Question 17

Which of the following best explains why the genetic code is described as 'nonoverlapping'?

Accepted Answer

Each nucleotide is part of only one codon.

Question 18

A bacterial gene cluster produces a single mRNA that encodes several proteins. What is this type of mRNA called?

Accepted Answer

Polycistronic mRNA

Question 19

Which process is illustrated by the equation $$	ext{DNA} ightarrow 	ext{RNA} ightarrow 	ext{Protein}$$?

Accepted Answer

Central dogma of molecular biology

Question 20

Which of the following is a real-world consequence of a mutation that introduces a premature stop codon in a gene encoding a critical enzyme?

Accepted Answer

The enzyme will be truncated and likely nonfunctional, potentially causing disease.

The Genetic Code and Transcription: Structure, Function, and Regulation

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