Question 1

Which of the following best describes the genetic code as it relates to translation?

Accepted Answer

It is a linear sequence of ribonucleotides in mRNA, read in triplets, that specifies amino acids during translation.

Question 2

How many possible codons can be formed from the four RNA nucleotides if codons are three nucleotides long?

Accepted Answer

$$4^3 = 64$

Question 3

Which codon serves as the universal start signal for translation in most organisms?

Accepted Answer

AUG

Question 4

A mutation changes the codon UAU (tyrosine) to UAA. What is the likely effect on translation?

Accepted Answer

Translation will terminate prematurely due to the introduction of a stop codon.

Question 5

Which property of the genetic code allows multiple codons to specify the same amino acid?

Accepted Answer

Degenerate

Question 6

What experimental evidence first demonstrated that UUU codes for phenylalanine?

Accepted Answer

A cell-free system using poly(U) mRNA produced a protein containing only phenylalanine.

Question 7

Which of the following codons is NOT a stop codon?

Accepted Answer

AUG

Question 8

Why is the genetic code described as 'non-overlapping'?

Accepted Answer

Each nucleotide is part of only one codon in a given reading frame.

Question 9

Which experimental method allowed scientists to determine the amino acid specified by a given RNA triplet using ribosomes and tRNA?

Accepted Answer

Triplet binding assay

Question 10

If a synthetic mRNA contains only the bases C and A in a 1:5 ratio, and 69% of the resulting protein is proline, what does this suggest about the codons for proline?

Accepted Answer

Proline is coded by triplets with mostly cytosines, such as CCC and CCA.

Question 11

Which statement best explains the 'wobble hypothesis' in tRNA-codon pairing?

Accepted Answer

The third base of the codon can pair with more than one base in the anticodon, allowing flexibility.

Question 12

Which of the following is a direct result of the genetic code being nearly universal?

Accepted Answer

Genes from one species can be expressed in another species, such as GFP from jellyfish in zebrafish.

Question 13

A scientist synthesizes an mRNA with the sequence 5'-AUGGCCUAA-3'. What is the resulting amino acid sequence?

Accepted Answer

Met-Ala

Question 14

Which property of the genetic code ensures that once translation begins, codons are read continuously without interruption?

Accepted Answer

Commaless

Question 15

If the codon on mRNA is 5'-UCU-3', which anticodon on tRNA would pair with it according to standard base pairing?

Accepted Answer

3'-AGA-5'

Question 16

Which of the following best describes the outcome of the triplet binding assay?

Accepted Answer

It identified which amino acid is specified by a given RNA triplet by observing tRNA binding to ribosomes.

Question 17

A mutation changes the third base of a codon from C to U, but the same amino acid is still incorporated. What property of the genetic code does this illustrate?

Accepted Answer

Degenerate

Question 18

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

Accepted Answer

It is ambiguous.

Question 19

In a cell-free translation system, which of the following would result if only poly(A) mRNA is added?

Accepted Answer

A polypeptide containing only lysine residues.

Question 20

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

Accepted Answer

Each codon specifies only one amino acid.

The Genetic Code and Transcription: Study Notes for Genetics Students

Study Guide - Practice Questions

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