Question 1

Which of the following statements best describes the wobble rule in codon-anticodon recognition?

Accepted Answer

Wobble allows non-standard base pairing at the third position of the codon, enabling one tRNA to recognize multiple codons for the same amino acid.

Question 2

A mutation changes the codon $$GAA ($$glutamic acid) to $$GAG in a $$human gene. What type of mutation is this, and what is the likely effect?

Accepted Answer

Synonymous mutation; does not change the amino acid and is likely silent.

Question 3

Which of the following is TRUE regarding the universality of the genetic code?

Accepted Answer

The genetic code is nearly universal, but exceptions exist in some prokaryotes, fungi, and protists.

Question 4

A patient has a mutation in the MDR1 gene that changes a common codon to a rare synonymous codon. What is a possible consequence of this mutation?

Accepted Answer

Translation may be slower, potentially affecting protein folding and substrate specificity.

Question 5

Which enzyme is responsible for attaching amino acids to tRNAs, and what energy source does it use?

Accepted Answer

Aminoacyl-tRNA synthetase; uses energy from ATP.

Question 6

Which of the following codons is recognized by a protein release factor rather than a tRNA during translation termination in bacteria?

Accepted Answer

$$UAA$$

Question 7

A conservative mutation is best defined as:

Accepted Answer

A mutation that changes a codon to one encoding a chemically similar amino acid, often preserving protein function.

Question 8

Which of the following statements about synonymous mutations is FALSE?

Accepted Answer

Synonymous mutations always have no effect on protein function.

Question 9

If a nonsense mutation introduces a premature stop codon in an mRNA, which genetic mechanism can allow translation to continue past this stop codon?

Accepted Answer

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

Question 10

Which of the following best explains why codon usage bias can affect protein expression in different organisms?

Accepted Answer

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

Question 11

Which of the following is NOT a consequence of the degeneracy of the genetic code?

Accepted Answer

One codon can encode multiple amino acids.

Question 12

A mutation changes the codon $$AAA ($$lysine) to $$AAG ($$also lysine). In E. coli, $$AAA is $$used much more frequently than $$AAG. $$What is a possible effect of this mutation?

Accepted Answer

Slower translation due to lower abundance of tRNA for $$AAG$$, potentially affecting protein folding.

Question 13

Which of the following statements about tRNA recognition by aminoacyl-tRNA synthetases is correct?

Accepted Answer

Recognition involves a specific set of nucleotides called the tRNA 'identity set', often found in the acceptor stem and anticodon loop.

Question 14

Which of the following is an example of a missense mutation that is NOT conservative?

Accepted Answer

A mutation that changes a codon for glycine to a codon for tryptophan.

Question 15

Which of the following is TRUE about suppressor tRNAs?

Accepted Answer

Suppressor tRNAs can recognize mutated codons and insert amino acids, allowing translation to continue past mutations.

Question 16

During translation, which of the following events occurs during the elongation phase?

Accepted Answer

Peptide bond formation and translocation of the ribosome along the mRNA.

Question 17

Which of the following is a property of the genetic code that helps minimize the effects of mutations?

Accepted Answer

Codons for chemically similar amino acids are often similar, so conservative mutations may preserve protein function.

Question 18

Which of the following statements about translation termination is correct?

Accepted Answer

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

Question 19

A mutation in the anticodon of a tRNA allows it to recognize a mutated codon in mRNA and insert the original amino acid. What is this type of genetic event called?

Accepted Answer

Suppressor mutation.

Question 20

Which of the following equations correctly represents the two-step reaction catalyzed by aminoacyl-tRNA synthetase?

Accepted Answer

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

Genetic Code, Translation, and Mutation: Structure and Function

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