Question 1

Which of the following best describes the main finding of Beadle and Tatum’s experiments with Neurospora crassa?

Accepted Answer

Each gene encodes a specific enzyme that affects a single step in a metabolic pathway.

Question 2

Why was the 'one gene—one enzyme' hypothesis revised to the 'one gene—one polypeptide' hypothesis?

Accepted Answer

Because not all proteins are enzymes, and some proteins are made of multiple polypeptides encoded by different genes.

Question 3

Which of the following statements correctly distinguishes RNA from DNA?

Accepted Answer

RNA contains uracil instead of thymine.

Question 4

Which arrow in the following flow chart represents the process of transcription?

$$	ext{DNA} \xrightarrow{?} 	ext{mRNA} \xrightarrow{?} 	ext{Protein}$$

Accepted Answer

The arrow from DNA to mRNA

Question 5

Which of the following best explains why the genetic code is described as 'redundant but not ambiguous'?

Accepted Answer

Multiple codons can specify the same amino acid, but each codon specifies only one amino acid.

Question 6

A mutation causes a single nucleotide change in a gene, resulting in a premature stop codon. What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; likely results in a truncated, nonfunctional protein.

Question 7

Which of the following best describes the role of the promoter in transcription?

Accepted Answer

It is the region where RNA polymerase binds to initiate transcription.

Question 8

In eukaryotic cells, which of the following modifications occurs to pre-mRNA before it becomes mature mRNA?

Accepted Answer

Addition of a 5' cap, addition of a poly-A tail, and removal of introns

Question 9

Which of the following statements about ribozymes is correct?

Accepted Answer

Ribozymes are RNA molecules that function as enzymes.

Question 10

Which of the following best explains the evolutionary significance of introns?

Accepted Answer

Introns allow for alternative splicing, increasing protein diversity.

Question 11

Which of the following best describes the function of tRNA during translation?

Accepted Answer

tRNA carries amino acids to the ribosome and matches them to the coded mRNA message.

Question 12

What determines whether a ribosome will be free in the cytoplasm or attached to the rough endoplasmic reticulum?

Accepted Answer

The presence of a signal peptide in the growing polypeptide chain.

Question 13

Which of the following best describes a frameshift mutation and its likely effect?

Accepted Answer

A mutation that inserts or deletes nucleotides not in multiples of three, altering the reading frame and likely resulting in a nonfunctional protein.

Question 14

Which of the following is true regarding the location of transcription and translation in prokaryotes versus eukaryotes?

Accepted Answer

Transcription occurs in the nucleus and translation in the cytoplasm in eukaryotes.

Question 15

A patient is diagnosed with sickle cell anemia, which is caused by a single nucleotide substitution in the hemoglobin gene. What type of mutation is this, and what is its effect?

Accepted Answer

Missense mutation; changes one amino acid, altering protein function.

Question 16

Rank the following mutations from greatest to least impact on protein structure and function: frameshift, nonsense, missense, silent.

Accepted Answer

Frameshift \u003e nonsense \u003e missense \u003e silent

Question 17

Which of the following best describes the process of translation initiation in eukaryotes?

Accepted Answer

The small ribosomal subunit binds to the 5' cap of mRNA and scans for the start codon.

Question 18

Which of the following statements about the reading frame during translation is correct?

Accepted Answer

The reading frame is established by the first AUG codon and determines how codons are grouped.

Question 19

Which of the following is a correct description of a codon?

Accepted Answer

A sequence of three nucleotides on mRNA that codes for a specific amino acid.

Question 20

Which of the following best describes how tRNA is joined to the appropriate amino acid?

Accepted Answer

By the enzyme aminoacyl-tRNA synthetase, which catalyzes the attachment using ATP.

Gene Expression: From Gene to Protein (Chapter 17) – Study Notes

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