Question 1

Which of the following correctly describes the difference between purines and pyrimidines in DNA structure?

Accepted Answer

Purines have a double-ring structure (adenine and guanine), while pyrimidines have a single-ring structure (cytosine and thymine).

Question 2

Which of the following best explains why DNA strands are described as antiparallel?

Accepted Answer

The two strands run in opposite directions: one 5' to 3', the other 3' to 5'.

Question 3

During transcription in eukaryotes, which of the following sequences is recognized by RNA polymerase to initiate transcription?

Accepted Answer

TATA box

Question 4

Which scientist(s) provided the first experimental evidence that DNA is the genetic material by using bacteriophages?

Accepted Answer

Hershey and Chase

Question 5

A mutation changes a codon from UAU (tyrosine) to UAA. What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; introduces a premature stop codon, likely truncating the protein

Question 6

Which of the following statements about RNA and DNA is correct?

Accepted Answer

RNA contains uracil instead of thymine, and is usually single-stranded.

Question 7

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

Accepted Answer

A site

Question 8

A frameshift mutation occurs due to the insertion of a single nucleotide in the coding region of a gene. What is the most likely consequence for the resulting protein?

Accepted Answer

The reading frame is shifted, potentially altering every amino acid downstream of the mutation.

Question 9

In the lac operon, what happens to cAMP levels and transcription when glucose is low and lactose is present?

Accepted Answer

cAMP levels are high, CAP binds to the promoter, and transcription of the lac operon increases.

Question 10

Which of the following best describes the function of snRNPs in eukaryotic cells?

Accepted Answer

They are involved in the splicing of pre-mRNA by recognizing and removing introns.

Question 11

Which of the following modifications to histones is associated with increased gene expression in eukaryotes?

Accepted Answer

Histone acetylation

Question 12

A mutation in the TATA box of a gene's promoter region would most likely result in which of the following?

Accepted Answer

Reduced or abolished transcription initiation due to impaired binding of transcription factors

Question 13

Which of the following best explains why the genetic code is described as 'wobble' at the third position of the codon?

Accepted Answer

The third base of the codon can pair with more than one base in the anticodon, allowing some tRNAs to recognize multiple codons.

Question 14

Which of the following is true regarding the directionality of RNA polymerase during transcription?

Accepted Answer

RNA polymerase synthesizes RNA in the 5' to 3' direction.

Question 15

Which of the following is a real-world example of gene regulation in eukaryotes involving enhancers?

Accepted Answer

Switches controlling Pitx1 gene expression in stickleback fish, where enhancers bind activators to regulate transcription in specific tissues

Question 16

A patient is found to have a point mutation in a gene that does not change the amino acid sequence of the encoded protein. What type of mutation is this?

Accepted Answer

Silent mutation

Question 17

Which of the following best describes the role of GTP during translation?

Accepted Answer

GTP is used as an energy source for peptide bond formation and translocation of the ribosome.

Question 18

In the context of the trp operon, what is the effect of tryptophan binding to the repressor protein?

Accepted Answer

It causes a conformational change in the repressor, enabling it to bind the operator and block transcription.

Question 19

Which of the following best explains the difference between exons and introns in eukaryotic genes?

Accepted Answer

Exons are coding regions retained in mature mRNA, while introns are non-coding regions removed during RNA splicing.

Molecular Genetics: DNA, RNA, Transcription, Translation, Mutations, and Gene Regulation

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