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 first arrow, from DNA to mRNA

Question 5

Which of the following best describes the difference between transcription and translation?

Accepted Answer

Transcription produces an RNA copy of a gene, while translation uses mRNA to synthesize a polypeptide.

Question 6

In eukaryotic cells, where do transcription and translation occur, respectively?

Accepted Answer

Transcription occurs in the nucleus; translation occurs in the cytoplasm.

Question 7

What is a codon, and how does it relate to the sequence of amino acids in a polypeptide?

Accepted Answer

A codon is a sequence of three nucleotides on mRNA that specifies a particular amino acid.

Question 8

Which statement 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 9

Why is maintaining the correct reading frame during translation critical for protein synthesis?

Accepted Answer

Because shifting the reading frame changes the grouping of codons, potentially altering every amino acid downstream.

Question 10

How does RNA polymerase recognize where to begin transcription on a DNA molecule?

Accepted Answer

It binds to a specific DNA sequence called the promoter.

Question 11

Which of the following correctly lists the steps of transcription in order?

Accepted Answer

Initiation, Elongation, Termination

Question 12

Which of the following is NOT a typical modification made to eukaryotic pre-mRNA after transcription?

Accepted Answer

Addition of a 3' guanine cap

Question 13

What is a ribozyme?

Accepted Answer

An RNA molecule that functions as an enzyme.

Question 14

What is the evolutionary significance of introns in eukaryotic genes?

Accepted Answer

They allow for alternative splicing, increasing protein diversity.

Question 15

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 16

How is a tRNA molecule joined to its correct amino acid?

Accepted Answer

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

Question 17

Which of the following 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.

Question 18

Which of the following statements about protein synthesis in prokaryotes and eukaryotes is correct?

Accepted Answer

In prokaryotes, transcription and translation are coupled and can occur simultaneously.

Question 19

Which of the following is a point mutation?

Accepted Answer

A change in a single nucleotide pair in DNA.

Question 20

Rank the following mutations from greatest to least impact on gene product function: frameshift, nonsense, missense, silent. Which is the correct order?

Accepted Answer

Frameshift \u003e Nonsense \u003e Missense \u003e Silent

Gene Expression: From Gene to Protein – Study Notes

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