Question 1

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

Accepted Answer

Information flows from DNA to RNA to protein.

Question 2

A scientist discovers a new organism and analyzes its genetic code. She finds that the codon AUG codes for methionine, and UAA, UAG, and UGA do not code for any amino acid. What does this suggest about the genetic code?

Accepted Answer

The genetic code is universal among living organisms.

Question 3

During transcription, which direction is the RNA strand synthesized?

Accepted Answer

5' → 3'

Question 4

Which of the following is NOT a function of mRNA modifications after transcription?

Accepted Answer

Increasing the number of exons in the mRNA

Question 5

A mutation changes the DNA sequence from $	ext{ATG}$ to $	ext{ATA}$ in the coding region of a gene. If $	ext{ATG}$ codes for methionine (start codon) and $	ext{ATA}$ codes for isoleucine, what is the most likely effect on translation?

Accepted Answer

Translation will not initiate at this site, possibly preventing protein synthesis.

Question 6

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

Accepted Answer

Some amino acids are specified by more than one codon.

Question 7

A patient has a genetic disorder caused by improper removal of introns from pre-mRNA. Which process is most likely defective?

Accepted Answer

RNA splicing

Question 8

Which of the following codons is a stop codon in the genetic code?

Accepted Answer

UGA

Question 9

If a gene contains 5 exons and 4 introns, how many regions will be joined together in the mature mRNA after splicing?

Accepted Answer

5

Question 10

Which of the following statements about DNA and RNA is correct?

Accepted Answer

DNA is usually double-stranded, while RNA is usually single-stranded.

Question 11

A researcher is studying a gene with the following DNA sequence: $	ext{3'-TACGGT-5'}$. What is the corresponding mRNA sequence produced during transcription?

Accepted Answer

$	ext{5'-AUGCCA-3'}$

Question 12

Which stage of transcription involves the assembly of molecules at the promoter and the beginning of RNA synthesis?

Accepted Answer

Initiation

Question 13

Why is the genetic code described as 'commaless'?

Accepted Answer

There are no indicators to mark the end of one codon and the beginning of the next.

Question 14

Which of the following is true regarding the start codon in mRNA translation?

Accepted Answer

It is AUG, which codes for methionine.

Question 15

A mutation in a gene results in the loss of the 5' cap on the mRNA. Which of the following is a likely consequence?

Accepted Answer

Ribosomes may have difficulty attaching to the mRNA.

Question 16

Which of the following best describes the role of exons in eukaryotic genes?

Accepted Answer

They are coding regions that are usually translated into amino acid sequences.

Question 17

If a single nucleotide change converts a sense codon into a stop codon, what type of mutation has occurred?

Accepted Answer

Nonsense mutation

Question 18

Which of the following is true about the number of codons and amino acids?

Accepted Answer

There are 64 codons, but only 20 amino acids.

Question 19

A gene is transcribed and the resulting pre-mRNA contains both exons and introns. What must occur before this mRNA can be translated?

Accepted Answer

The introns must be removed and exons joined together.

Question 20

Which of the following best explains why only methionine and tryptophan are specified by a single codon?

Accepted Answer

All other amino acids are specified by more than one codon due to degeneracy.

Gene Expression: From DNA to Protein

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