Question 1

Which of the following best explains why transcription and translation can occur simultaneously in bacteria but not in eukaryotes?

Accepted Answer

Bacteria lack a nuclear envelope, so ribosomes can access mRNA as it is being transcribed.

Question 2

A mutation changes the DNA sequence from 5'-ATG-3' to 5'-ATA-3'. What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Missense mutation; it changes one amino acid in the protein.

Question 3

During eukaryotic transcription, which sequence signals the end of transcription and leads to the release of pre-mRNA?

Accepted Answer

The polyadenylation signal sequence $$\mathrm{AAUAAA}$$

Question 4

Which of the following best describes the function of the spliceosome during RNA processing in eukaryotes?

Accepted Answer

It removes introns and joins exons to produce mature mRNA.

Question 5

A scientist observes that a single nucleotide insertion occurs in the coding region of a gene. What is the most likely consequence of this mutation?

Accepted Answer

A frameshift mutation, altering the reading frame and likely resulting in a nonfunctional protein.

Question 6

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

Accepted Answer

It is degenerate, meaning more than one codon can specify the same amino acid.

Question 7

During translation, what is the role of aminoacyl-tRNA synthetase?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA using ATP hydrolysis.

Question 8

A patient has a genetic disorder caused by a mutation that introduces a premature stop codon in a critical gene. What type of mutation is this, and what is the likely effect?

Accepted Answer

Nonsense mutation; it results in a truncated, nonfunctional protein.

Question 9

Which of the following best explains why the genetic code must be read in the correct reading frame?

Accepted Answer

A shift in the reading frame changes every codon downstream, altering the entire amino acid sequence.

Question 10

Which of the following is a key difference between transcription in bacteria and eukaryotes?

Accepted Answer

Eukaryotic RNA polymerase II requires transcription factors to initiate transcription, while bacterial RNA polymerase does not.

Question 11

A researcher mutates the TATA box in a eukaryotic gene's promoter. What is the most likely effect on transcription?

Accepted Answer

Transcription initiation will be impaired because transcription factors cannot bind efficiently.

Question 12

Which of the following best describes the process of translation elongation in eukaryotes?

Accepted Answer

Amino acids are added one by one to the growing polypeptide chain as the ribosome moves along the mRNA from 5' to 3'.

Question 13

Which of the following modifications occurs to eukaryotic pre-mRNA before it is exported from the nucleus?

Accepted Answer

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

Question 14

A gene has the following coding sequence: 5'-ATG GAA TGA-3'. If a single nucleotide is deleted after the start codon, what is the resulting effect?

Accepted Answer

A frameshift mutation, likely resulting in a nonfunctional protein.

Question 15

Which of the following statements about ribosomes is correct?

Accepted Answer

They are composed of proteins and rRNA and facilitate the coupling of tRNA anticodons with mRNA codons.

Question 16

Which of the following best explains why a silent mutation does not affect the protein sequence?

Accepted Answer

The genetic code is degenerate, so multiple codons can code for the same amino acid.

Question 17

In a real-world scenario, a patient is exposed to a mutagen that causes frequent point mutations. Which of the following is NOT a possible outcome of these mutations?

Accepted Answer

All point mutations will result in a nonfunctional protein.

Question 18

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

Accepted Answer

The genetic code is nearly universal among all organisms, allowing genes to be transferred between species.

Question 19

During translation, what event occurs when a stop codon enters the A site of the ribosome?

Accepted Answer

A release factor binds, hydrolyzing the bond between the polypeptide and tRNA, releasing the completed protein.

Ch. 17: Gene Expression: From DNA to Protein

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