Q: If the mRNA sequence is $$5'\text{-}AUG\,CCU\,GAA\,UUC\,UGA\text{-}3'$$, what is the corresponding amino acid sequence produced during translation?

$$\mathrm{Met\text{-}Pro\text{-}Glu\text{-}Phe}$$

Question 1

Which of the following best describes the 'one gene-one enzyme' hypothesis as demonstrated by Beadle and Tatum's experiments with Neurospora crassa?

Accepted Answer

Each gene encodes a single enzyme that catalyzes a specific step in a metabolic pathway.

Question 2

During transcription in eukaryotes, which of the following modifications occurs to the pre-mRNA before it becomes mature mRNA?

Accepted Answer

Addition of a 5' cap, splicing out of introns, and addition of a poly-A tail

Question 3

A mutation changes a codon from $$\mathrm{UAC} ($$tyrosine) to $$\mathrm{UAA}. $$What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; introduces a premature stop codon

Question 4

Which of the following statements about the genetic code is TRUE?

Accepted Answer

The genetic code is universal, with few exceptions across species.

Question 5

If the mRNA sequence is $$5'	ext{-}AUG\,CCU\,GAA\,UUC\,UGA	ext{-}3'$$, what is the corresponding amino acid sequence produced during translation?

Accepted Answer

$$\mathrm{Met	ext{-}Pro	ext{-}Glu	ext{-}Phe}$$

Question 6

Which of the following best explains why a frameshift mutation is often more severe than a missense mutation?

Accepted Answer

Frameshift mutations alter the reading frame, potentially changing every amino acid downstream.

Question 7

What is the role of tRNA during translation?

Accepted Answer

tRNA brings specific amino acids to the ribosome by matching its anticodon to the mRNA codon.

Question 8

Which of the following is a function of the 5' cap added to eukaryotic mRNA during processing?

Accepted Answer

It helps protect mRNA from degradation and assists in ribosome binding.

Question 9

A scientist introduces a mutation in the gene encoding an enzyme in the arginine biosynthesis pathway of Neurospora. The mutant strain can grow only if citrulline or arginine is supplied, but not if only ornithine is supplied. Where is the likely block in the pathway?

Accepted Answer

The enzyme converting ornithine to citrulline is defective.

Question 10

Which of the following best describes the process of translation?

Accepted Answer

Synthesis of a polypeptide using the information in mRNA.

Question 11

Which of the following is NOT a step in eukaryotic mRNA processing?

Accepted Answer

Attachment of amino acids to the mRNA

Question 12

A mutation in the spliceosome machinery would most likely affect which process?

Accepted Answer

Removal of introns from pre-mRNA

Question 13

Which of the following codons is a start codon in most organisms?

Accepted Answer

$$\mathrm{AUG}$$

Question 14

If a gene is mutated such that its mRNA now contains a premature stop codon, what is the most likely result?

Accepted Answer

A truncated, likely nonfunctional protein is produced.

Question 15

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

Accepted Answer

Some amino acids are specified by more than one codon.

Question 16

Which of the following is a real-world example of a disease caused by a single gene mutation affecting protein function?

Accepted Answer

Phenylketonuria (PKU), caused by a mutation in the gene encoding phenylalanine hydroxylase

Question 17

Which of the following statements about ribosomes is TRUE?

Accepted Answer

Ribosomes are composed of rRNA and proteins and are the site of protein synthesis.

Question 18

A patient is found to have a mutation that prevents the addition of a poly-A tail to mRNA. Which of the following is a likely consequence?

Accepted Answer

The mRNA will be rapidly degraded in the cytoplasm.

Question 19

Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes one amino acid to another in the protein sequence.

Gene Expression: From Gene to Protein – Study Notes

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