Question 1

Which feature of the genetic code allows multiple codons to specify the same amino acid, and what is the evolutionary advantage of this feature?

Accepted Answer

Degenerate; it reduces the impact of point mutations by allowing silent mutations.

Question 2

A frameshift mutation occurs when a single nucleotide is inserted into a DNA sequence. What is the most likely outcome for the resulting protein?

Accepted Answer

The reading frame will shift, resulting in a completely different amino acid sequence downstream.

Question 3

Which codon serves as the universal start signal for translation in most organisms, and what amino acid does it encode?

Accepted Answer

AUG; methionine

Question 4

In the triplet binding assay, what is the role of the ribosome?

Accepted Answer

It binds to a single codon and facilitates the binding of a complementary charged tRNA.

Question 5

A mutation changes a codon from UAU (tyrosine) to UAA. What is the consequence of this mutation?

Accepted Answer

Translation will terminate prematurely, resulting in a truncated protein.

Question 6

Which equation best represents the relationship between the number of possible codons and the number of nucleotide bases in the triplet code?

Accepted Answer

$$4^3$$

Question 7

What is the function of the sigma ($$\sigma) $$factor in bacterial transcription?

Accepted Answer

It recognizes and binds to promoter sequences, facilitating RNA polymerase binding.

Question 8

Which of the following statements about the wobble hypothesis is correct?

Accepted Answer

The third base of the codon can pair with multiple bases in the anticodon, allowing flexibility.

Question 9

Which posttranscriptional modification is essential for protecting eukaryotic mRNA from degradation?

Accepted Answer

Addition of a poly-A tail at the 3' end

Question 10

A piece of mRNA reads 5' AUG-UUA-UAA-CCC 3'. What would the cell translate that as?

Accepted Answer

Met-Leu

Question 11

Which of the following is NOT a feature of the genetic code?

Accepted Answer

It is ambiguous.

Question 12

What is the role of snRNPs in eukaryotic cells?

Accepted Answer

They are essential components of the spliceosome, facilitating intron removal.

Question 13

Which RNA polymerase is responsible for transcribing protein-coding genes in eukaryotes?

Accepted Answer

RNA polymerase II

Question 14

Which of the following best describes alternative splicing?

Accepted Answer

It allows a single gene to produce multiple mature mRNAs by varying exon inclusion.

Question 15

In human mitochondria, the codon UGA encodes which amino acid?

Accepted Answer

Tryptophan

Question 16

Which of the following is a consensus sequence found in E. coli promoters?

Accepted Answer

TTGACA and TATAAT

Question 17

What is the effect of a nonsense mutation in a gene?

Accepted Answer

It causes premature termination of translation, producing a truncated protein.

Question 18

Which of the following statements about polycistronic mRNA is correct?

Accepted Answer

It encodes multiple proteins from a single mRNA molecule in bacteria.

Question 19

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

Accepted Answer

Most organisms use the same codon assignments, but some exceptions exist in mitochondria and certain protists.

Question 20

Which of the following is a real-life application of understanding the triplet nature of the genetic code?

Accepted Answer

Designing synthetic mRNAs for in vitro translation to produce specific proteins.

Ch 12 The Genetic Code and Transcription: Structure, Function, and Mechanisms

Study Guide - Practice Questions