Question 1

Which statement best describes the central dogma of molecular biology?

Accepted Answer

Genetic information flows from DNA to RNA to proteins.

Question 2

During translation, how many nucleotides make up a codon, and what does each codon specify?

Accepted Answer

Three nucleotides; each codon specifies an amino acid.

Question 3

Which of the following is a feature of the genetic code that helps minimize the effects of point mutations?

Accepted Answer

The code is degenerate.

Question 4

A mutation changes the third base of the codon GAA to GAG. Both codons code for glutamate. What property of the genetic code does this illustrate?

Accepted Answer

Degeneracy

Question 5

In prokaryotes, what sequence precedes the start codon and helps initiate translation?

Accepted Answer

Shine-Dalgarno sequence

Question 6

Which codon is most commonly used as the start signal for protein synthesis in both prokaryotes and eukaryotes?

Accepted Answer

AUG

Question 7

A scientist discovers a new organism whose mitochondria use UGA to code for tryptophan instead of a stop signal. What does this observation best illustrate?

Accepted Answer

Mitochondria can have variations in the genetic code.

Question 8

Which of the following best describes the directionality of the genetic code during translation?

Accepted Answer

It is read from the 5' end to the 3' end of mRNA.

Question 9

A patient has a mutation in the Shine-Dalgarno sequence of a bacterial gene. What is the most likely effect on protein synthesis?

Accepted Answer

The ribosome may not properly bind to the mRNA, reducing translation efficiency.

Question 10

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

Accepted Answer

Each amino acid is encoded by only one codon.

Question 11

If a eukaryotic mRNA has multiple AUG codons, which one is typically used as the start codon?

Accepted Answer

The AUG nearest the 5' end

Question 12

Which of the following best explains why the genetic code is described as 'non-overlapping'?

Accepted Answer

Each nucleotide is part of only one codon.

Question 13

A mutation changes an AGA codon to AGG in human mitochondria. What is the likely result?

Accepted Answer

Both codons are stop codons, so translation will terminate.

Question 14

Which of the following is a real-life consequence of the degeneracy of the genetic code?

Accepted Answer

Some mutations in the third base of a codon do not change the amino acid sequence of the protein.

Question 15

Which of the following equations correctly represents the number of possible codons in the genetic code?

Accepted Answer

$$4^3$$

Question 16

A researcher is studying a gene with the following mRNA sequence near the 5' end: 5'-GCCGCCGCCGCCGCCGCCAUGGAG...-3'. Which codon is most likely the start codon?

Accepted Answer

AUG

Question 17

Which of the following best describes the role of the Shine-Dalgarno sequence in prokaryotic translation?

Accepted Answer

It helps align the ribosome with the start codon.

Question 18

If a mutation introduces a premature UGA codon in a human mitochondrial gene, what is the likely outcome?

Accepted Answer

Tryptophan will be incorporated at that position.

Question 19

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

Accepted Answer

It is read from 3' to 5'.

Question 20

A patient’s cells are found to use AUA as a start codon in their mitochondria. What amino acid is incorporated at this position?

Accepted Answer

Methionine

Chapter 4: DNA, RNA, and the Flow of Genetic Information

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