Question 1

Which of the following statements best describes the redundancy (degeneracy) of the genetic code?

Accepted Answer

Multiple codons can encode the same amino acid, often differing at the third nucleotide position.

Question 2

A mutation changes the codon GAA to GAG in an mRNA sequence. Both codons encode glutamic acid. What type of mutation is this?

Accepted Answer

Synonymous (silent) mutation

Question 3

Which of the following is TRUE regarding the wobble hypothesis in codon-anticodon recognition?

Accepted Answer

Wobble pairing allows a single tRNA to recognize multiple codons for the same amino acid.

Question 4

A nonsense mutation introduces a premature stop codon in an mRNA. Which genetic mechanism can suppress this effect and allow translation to continue?

Accepted Answer

A nonsense suppressor tRNA with a mutated anticodon that recognizes the stop codon and inserts an amino acid.

Question 5

Which of the following is NOT a function of aminoacyl-tRNA synthetases?

Accepted Answer

Catalyzing peptide bond formation between amino acids during translation.

Question 6

In most organisms, codon usage bias can affect which of the following processes?

Accepted Answer

The efficiency and speed of translation due to differential tRNA abundance.

Question 7

Which statement about conservative mutations is correct?

Accepted Answer

They change the encoded amino acid to one with similar biochemical properties, often minimizing effects on protein function.

Question 8

A 'silent' polymorphism in the MDR1 gene changes substrate specificity of the protein. What is the most likely explanation for this phenomenon?

Accepted Answer

The synonymous mutation alters the mRNA sequence, which can affect translation speed and protein folding.

Question 9

Which of the following codons is recognized by protein release factors, not by tRNAs, during translation termination in bacteria?

Accepted Answer

UAA

Question 10

If a tRNA anticodon mutates so that it can recognize a mutated codon and insert the original amino acid, what is this tRNA called?

Accepted Answer

Suppressor tRNA

Question 11

Which equation best represents the energy requirement for aminoacyl-tRNA synthetase activity?

Accepted Answer

$$\mathrm{Amino~acid} + \mathrm{tRNA} + \mathrm{ATP} \rightarrow \mathrm{Aminoacyl{-}tRNA} + \mathrm{AMP} + \mathrm{PP_i}$$

Question 12

Which of the following is a consequence of the universality of the genetic code?

Accepted Answer

Genes from one organism can often be expressed in another organism, producing the same protein sequence.

Question 13

Which of the following statements about synonymous mutations is FALSE?

Accepted Answer

They always have no effect on protein function.

Question 14

Which of the following best explains why codon usage bias exists in different organisms?

Accepted Answer

Different organisms have different abundances of tRNAs for specific codons, affecting translation efficiency.

Question 15

Which of the following is TRUE about the recognition of stop codons during translation?

Accepted Answer

Stop codons are recognized by protein release factors, not by tRNAs.

Question 16

A mutation changes the codon AAA (lysine) to AGA (arginine). Which type of mutation is this?

Accepted Answer

Conservative missense mutation

Question 17

Which of the following statements about suppressor tRNAs is correct?

Accepted Answer

Suppressor tRNAs can recognize mutated codons and insert amino acids to restore protein function.

Question 18

Which of the following is NOT a general rule about codon-tRNA interactions?

Accepted Answer

Each codon can be recognized by tRNAs encoding different amino acids.

Question 19

Which of the following best describes the effect of a missense suppressor tRNA?

Accepted Answer

It recognizes a mutated codon and inserts the original or a similar amino acid, potentially restoring protein function.

Genetic Code and Translation: Structure, Function, and Mutation

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