Question 1

Which of the following best describes the 'central dogma' of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 2

A mutation in the gene encoding an enzyme required for pigment synthesis results in a white donkey instead of a brown one. What is the most direct molecular explanation for this change in phenotype?

Accepted Answer

The mutation leads to a nonfunctional enzyme, so pigment is not produced.

Question 3

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

Accepted Answer

The genetic code is ambiguous; a codon can specify more than one amino acid.

Question 4

During transcription in eukaryotes, which of the following is TRUE?

Accepted Answer

The template strand can be either DNA strand, depending on the gene.

Question 5

A DNA template strand has the sequence 3'-TACGGTACG-5'. What is the sequence of the mRNA transcribed from this region?

Accepted Answer

5'-AUGCCAUGC-3'

Question 6

Which of the following modifications occur to eukaryotic pre-mRNA before it leaves the nucleus?

Accepted Answer

Addition of a 5' cap and a poly-A tail

Question 7

What is the function of the 5' cap and poly-A tail added to eukaryotic mRNA?

Accepted Answer

They facilitate the export of mRNA from the nucleus, protect mRNA from degradation, and help with ribosome attachment.

Question 8

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

Accepted Answer

Some amino acids are encoded by more than one codon.

Question 9

A mutation changes the codon UAU (tyrosine) to UAA. What is the likely result of this mutation?

Accepted Answer

Translation will terminate prematurely, resulting in a truncated protein.

Question 10

Which of the following statements about tRNA is CORRECT?

Accepted Answer

tRNA molecules have an anticodon that is complementary to the mRNA codon.

Question 11

In eukaryotic cells, what is the correct sequence of events for gene expression?

Accepted Answer

Transcription → RNA processing → Translation

Question 12

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

In eukaryotes, transcription and translation are separated by the nuclear envelope.

Question 13

A scientist isolates a eukaryotic mRNA and finds that it contains both exons and introns. What is the best explanation?

Accepted Answer

The mRNA is a pre-mRNA and has not yet been processed.

Question 14

Which of the following best describes the role of the promoter in transcription?

Accepted Answer

It is a DNA sequence where RNA polymerase binds to initiate transcription.

Question 15

If the coding (non-template) DNA strand of a gene is 5'-ATG GGA TAA-3', what is the sequence of the mRNA produced?

Accepted Answer

5'-AUG GGA UAA-3'

Question 16

Which of the following is NOT a function of the poly-A tail in eukaryotic mRNA?

Accepted Answer

Signals the start of translation

Question 17

Which of the following statements about exons and introns is CORRECT?

Accepted Answer

Exons are expressed regions that code for protein, while introns are non-coding intervening sequences.

Question 18

A ribosome has three binding sites for tRNA. Which site holds the tRNA carrying the growing polypeptide chain?

Accepted Answer

P site

Question 19

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

Accepted Answer

A peptide bond forms between the amino acid in the A site and the growing polypeptide in the P site.

Question 20

A mutation in the promoter region of a gene reduces the binding of RNA polymerase. What is the most likely effect?

Accepted Answer

Transcription of the gene will decrease, leading to less protein produced.

Gene Expression: From a Gene to a Protein (Chapter 17 Study Notes)

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