Question 1

Which experiment provided the first strong evidence for the 'one gene-one enzyme' hypothesis, and what organism was used?

Accepted Answer

The experiment with Neurospora crassa (bread mold) using X-ray mutagenesis to identify mutants unable to grow on minimal medium.

Question 2

Alkaptonuria is a genetic disorder that results in dark urine due to the inability to break down a specific compound. This disorder was one of the first to suggest that genes control metabolic pathways. Which enzyme is missing in individuals with alkaptonuria?

Accepted Answer

Homogentisate oxidase

Question 3

In the arginine biosynthetic pathway studied in Neurospora, a mutant that can grow only when citrulline or arginine is added to the medium most likely has a defect in which enzyme?

Accepted Answer

Enzyme B (converts ornithine to citrulline)

Question 4

Which of the following best describes the process of gene expression?

Accepted Answer

DNA is transcribed to mRNA, which is then translated into protein.

Question 5

A DNA template strand has the sequence 3'-TAC TTC ACC CGT-5'. What is the corresponding mRNA sequence produced during transcription?

Accepted Answer

$$5' - AUG AAG UGG GCA - 3'$$

Question 6

Using the genetic code, what is the amino acid sequence translated from the mRNA strand $$5' - AUG AAG UGG GCA - 3'$$?

Accepted Answer

Met-Lys-Trp-Ala

Question 7

Which of the following statements about the universality of the genetic code is correct?

Accepted Answer

The genetic code is nearly universal, allowing genes from one organism to be expressed in another, such as bacteria producing human insulin.

Question 8

What is the main difference between gene expression in prokaryotes and eukaryotes?

Accepted Answer

Prokaryotes can couple transcription and translation, while eukaryotes modify RNA before translation.

Question 9

Which post-transcriptional modification is added to the 5' end of eukaryotic mRNA, and what is its function?

Accepted Answer

A 5' cap (modified guanine nucleotide) is added to protect the mRNA from degradation and help ribosome attachment.

Question 10

Alternative splicing allows a single gene to:

Accepted Answer

Produce multiple polypeptides by joining different combinations of exons.

Question 11

During translation, which site on the ribosome does the incoming aminoacyl-tRNA bind to?

Accepted Answer

A site

Question 12

A mutation changes a codon from $$UAC ($$tyrosine) to $$UAA ($$stop). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 13

Which of the following best describes a frameshift mutation?

Accepted Answer

An insertion or deletion of nucleotides that shifts the reading frame, often resulting in a nonfunctional protein.

Question 14

Which of the following is NOT a function of the 3' poly-A tail added during RNA processing?

Accepted Answer

It catalyzes peptide bond formation during translation.

Question 15

A patient with ornithine transcarbamylase (OTC) deficiency will have which pattern in the urea cycle metabolites?

Accepted Answer

High precursor, low citrulline, low arginine

Question 16

Which of the following best explains why bacteria can produce human insulin using recombinant DNA technology?

Accepted Answer

The universality of the genetic code allows bacterial cells to translate human genes into functional proteins.

Question 17

Which of the following is a silent mutation?

Accepted Answer

A nucleotide change that does not alter the amino acid sequence, such as $$CCG to$$ $$CCA$$ both coding for glycine.

Question 18

Which of the following is true about hemoglobin protein structure?

Accepted Answer

Hemoglobin is composed of multiple polypeptides encoded by different genes.

Question 19

Which step in gene expression involves the removal of introns and joining of exons?

Accepted Answer

RNA splicing

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

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