Question 1

Which of the following best describes the function of telomeres in human chromosomes?

Accepted Answer

They are repetitive DNA sequences at the ends of chromosomes that protect chromosome ends from degradation and fusion.

Question 2

A patient is diagnosed with myotonic dystrophy type 1 (DM1). Which genetic mechanism is most likely responsible for this disease?

Accepted Answer

An unstable expansion of a CTG trinucleotide repeat in the DMPK gene.

Question 3

Which of the following is a direct consequence of a mutation that disrupts the consensus sequence at a splice donor site?

Accepted Answer

The mRNA will be translated with a frameshift, potentially resulting in a nonfunctional protein.

Question 4

Which of the following best explains the phenomenon of 'genetic anticipation' observed in trinucleotide repeat expansion diseases?

Accepted Answer

The number of repeats increases in successive generations, leading to earlier onset and increased severity.

Question 5

A researcher finds a mutation in the promoter region of a gene. Which process is most likely to be directly affected?

Accepted Answer

Transcription initiation

Question 6

Which of the following equations correctly represents the number of possible codons in the genetic code, given that there are 4 different nucleotides and codons are three nucleotides long?

Accepted Answer

$$4^3 = 64$

Question 7

A patient with beta-thalassemia is found to have a mutation at a splice acceptor site in the beta-globin gene. What is the most likely molecular consequence?

Accepted Answer

Inclusion of intronic sequences in the mature mRNA, potentially causing a frameshift.

Question 8

Which of the following best describes the role of aminoacyl-tRNA synthetases in translation?

Accepted Answer

They catalyze the covalent attachment of amino acids to their corresponding tRNAs.

Question 9

A scientist is studying a gene with the following structure: promoter, 5' UTR, exon 1, intron, exon 2, 3' UTR. Which region is most likely to contain the poly-A signal sequence?

Accepted Answer

3' UTR

Question 10

Which of the following is a function of the 5' cap added to eukaryotic mRNA?

Accepted Answer

It facilitates ribosome binding during translation initiation.

Question 11

A mutation in the telomerase gene leads to reduced enzyme activity. Which clinical syndrome is most likely to result from this defect?

Accepted Answer

Dyskeratosis congenita

Question 12

Which of the following best explains why Dolly the sheep had shorter telomeres than expected for her age?

Accepted Answer

She was cloned from an adult somatic cell, which already had shortened telomeres.

Question 13

Which of the following best describes the function of enhancers in gene expression?

Accepted Answer

They bind specific transcription factors to increase transcriptional efficiency.

Question 14

A single base change near the translation start site of a gene results in a frameshift mutation. What is the most likely effect on the protein product?

Accepted Answer

The amino acid sequence will be altered from the mutation onward, likely resulting in a nonfunctional protein.

Question 15

Which of the following is true regarding the redundancy of the genetic code?

Accepted Answer

Most amino acids are encoded by more than one codon, often differing at the third nucleotide position.

Question 16

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

Accepted Answer

A-site

Question 17

Which of the following best describes the role of release factors in translation termination?

Accepted Answer

They mimic tRNA molecules and bind to stop codons, promoting release of the polypeptide chain.

Question 18

Which of the following is a characteristic feature of polyribosomes (polysomes)?

Accepted Answer

Multiple ribosomes simultaneously translating a single mRNA molecule.

Question 19

A mutation in the 3' UTR of a gene is most likely to affect which aspect of mRNA?

Accepted Answer

Stability and regulation of translation

Question 20

Which of the following best explains why telomerase inhibitors are being explored as cancer therapies?

Accepted Answer

They limit the ability of cancer cells to maintain telomere length, restricting their capacity for unlimited division.

Human Genome: Gene Structure and Function – Study Notes

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