Question 1

Which of the following best explains why codons are composed of three nucleotides?

Accepted Answer

Because a triplet code allows for 64 possible combinations, which is more than enough to specify all 20 amino acids.

Question 2

During translation, which molecule brings the correct amino acid to the ribosome based on the codon sequence of mRNA?

Accepted Answer

tRNA

Question 3

What is the function of the anticodon region of tRNA?

Accepted Answer

It base-pairs with the complementary codon on mRNA to ensure the correct amino acid is added.

Question 4

Which of the following best describes the role of ribosomal RNA (rRNA) in translation?

Accepted Answer

It forms the structural and catalytic core of the ribosome, facilitating peptide bond formation.

Question 5

A mutation changes the codon UAU (tyrosine) to UAA in an mRNA sequence. What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 6

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

Accepted Answer

It is nearly universal, meaning most organisms use the same codon assignments.

Question 7

Which process is catalyzed by a ribozyme during translation?

Accepted Answer

Peptide bond formation between amino acids

Question 8

What is the consequence of a frameshift mutation in a coding region of a gene?

Accepted Answer

It usually alters the reading frame, potentially changing every amino acid downstream and often resulting in a nonfunctional protein.

Question 9

During translation elongation, what happens immediately after a peptide bond is formed?

Accepted Answer

The polypeptide chain is transferred from the tRNA in the P site to the tRNA in the A site.

Question 10

Which of the following best describes the role of amino-acyl tRNA synthetase?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA.

Question 11

A ribosome has three binding sites for tRNA. Which site is responsible for accepting the incoming amino-acyl tRNA?

Accepted Answer

A site

Question 12

What triggers the termination of translation?

Accepted Answer

A stop codon enters the A site, causing a release factor to bind and promote hydrolysis of the polypeptide from the tRNA.

Question 13

Which of the following modifications can occur to a polypeptide after translation in the endomembrane system?

Accepted Answer

Addition of sugars, lipids, or phosphates, and removal of amino acids from the 5' end.

Question 14

If a mutation occurs in the DNA of a gametogenic cell during meiosis, what is a possible consequence?

Accepted Answer

The mutation will be inherited by offspring and may result in a genetic disorder.

Question 15

Which of the following is a silent mutation?

Accepted Answer

A mutation that changes a codon but does not alter the amino acid sequence of the protein.

Question 16

Which equation correctly represents the attachment of an amino acid to tRNA by amino-acyl tRNA synthetase?

Accepted Answer

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

Question 17

A patient has a mutation in the gene encoding the signal-recognition particle (SRP). Which cellular process is most likely to be affected?

Accepted Answer

Targeting of ribosomes to the endoplasmic reticulum for synthesis of secreted proteins

Question 18

Which of the following best describes the difference between free and bound ribosomes?

Accepted Answer

Free ribosomes synthesize proteins for use in the cytoplasm, while bound ribosomes synthesize proteins for secretion or use in organelles.

Question 19

Which of the following is NOT a function of the untranslated regions (UTRs) of mRNA?

Accepted Answer

They encode amino acids in the final protein.

Chapter 17: Transcription and Translation PART 2 (Gene Expression) – Study Notes

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