Question 1

Which of the following statements best explains why the genetic code is described as 'redundant but not ambiguous'?

Accepted Answer

More than one codon can specify the same amino acid, but no codon specifies more than one amino acid.

Question 2

A mutation changes the DNA sequence from 5'-TAC-3' to 5'-TAA-3'. What is the most likely effect on the resulting protein?

Accepted Answer

The protein will be prematurely terminated due to the introduction of a stop codon.

Question 3

During eukaryotic gene expression, which of the following modifications occurs to the pre-mRNA before it leaves the nucleus?

Accepted Answer

Addition of a 5' cap and a poly-A tail, and removal of introns.

Question 4

Which of the following best describes the role of tRNA during translation?

Accepted Answer

tRNA carries amino acids to the ribosome and matches them to the mRNA codon via its anticodon.

Question 5

In bacteria, translation can begin before transcription is finished. Which cellular feature allows this to occur?

Accepted Answer

Lack of a nuclear envelope, allowing ribosomes access to mRNA as it is being transcribed.

Question 6

A researcher observes that a single nucleotide insertion in a gene leads to a completely nonfunctional protein. What is the most likely explanation?

Accepted Answer

The insertion caused a frameshift mutation, altering the reading frame.

Question 7

Which of the following sequences represents a start codon in mRNA, and what amino acid does it code for?

Accepted Answer

$$\mathrm{AUG}$$, which codes for methionine

Question 8

Which of the following best describes the function of the poly-A tail added to eukaryotic mRNA?

Accepted Answer

It facilitates the export of mRNA from the nucleus and protects it from degradation.

Question 9

A point mutation changes a codon from $$\mathrm{GAA} to$$ $$\mathrm{GAG}$$, both of which code for glutamic acid. What type of mutation is this?

Accepted Answer

Silent mutation

Question 10

Which of the following events occurs during the elongation phase of translation?

Accepted Answer

A charged tRNA enters the A site, and a peptide bond forms between amino acids.

Question 11

Which of the following is true regarding the direction of RNA synthesis during transcription?

Accepted Answer

RNA is synthesized in the 5' to 3' direction.

Question 12

A patient is diagnosed with sickle-cell disease, which is caused by a single nucleotide substitution in the hemoglobin gene. What type of mutation is this?

Accepted Answer

Missense mutation

Question 13

Which of the following best describes the role of the release factor during translation termination?

Accepted Answer

It binds to the stop codon and causes the addition of a water molecule, releasing the polypeptide.

Question 14

Which of the following is a direct consequence of a frameshift mutation?

Accepted Answer

The reading frame of the mRNA is altered, potentially changing every amino acid downstream.

Question 15

Which of the following statements about ribosomes is correct?

Accepted Answer

Ribosomes facilitate the coupling of tRNA anticodons with mRNA codons during protein synthesis.

Question 16

Which of the following best explains why multiple ribosomes can translate a single mRNA molecule simultaneously in both bacteria and eukaryotes?

Accepted Answer

Ribosomes can attach to the mRNA as soon as the start codon is available, forming polyribosomes.

Question 17

Which of the following is NOT a function of the 5' cap added to eukaryotic mRNA?

Accepted Answer

Splicing together exons

Question 18

A gene contains the following sequence: 5'-ATG GAA TGA-3'. What is the corresponding mRNA sequence, and what is the resulting amino acid sequence?

Accepted Answer

mRNA: 5'-AUG GAA UGA-3'; Amino acids: Methionine-Glutamic acid-Stop

Question 19

Which of the following is true about the process of RNA splicing in eukaryotes?

Accepted Answer

Introns are removed and exons are joined together to form the mature mRNA.

Question 20

Which of the following best describes the energy source used during the elongation phase of translation?

Accepted Answer

GTP hydrolysis

Gene Expression: From Gene to Protein

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