Question 1

Which of the following statements best explains why DNA is considered antiparallel and how this property contributes to genetic integrity during replication?

Accepted Answer

Antiparallel orientation means one strand runs 5' to 3' and the other 3' to 5', enabling complementary base pairing and accurate template copying.

Question 2

Which base pairing is correct for DNA and RNA, and what is the consequence of a mismatch during replication?

Accepted Answer

In DNA, adenine pairs with thymine ($$A-T$$), and in RNA, adenine pairs with uracil ($$A-U$$); mismatches can lead to point mutations affecting protein function.

Question 3

During DNA replication, which enzyme is responsible for synthesizing the new DNA strand, and what is the direction of synthesis?

Accepted Answer

DNA polymerase; 5' to 3' direction.

Question 4

In a DNA replication fork, how are leading and lagging strands identified, and what is the role of Okazaki fragments?

Accepted Answer

The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously as Okazaki fragments in the 5' to 3' direction.

Question 5

Which process describes the synthesis of RNA from a DNA template, and what is the main enzyme involved?

Accepted Answer

Transcription; RNA polymerase.

Question 6

Which of the following is NOT a typical RNA processing event in eukaryotes?

Accepted Answer

Removal of exons.

Question 7

A mutation changes a codon from $$UAC ($$tyrosine) to $$UAA ($$stop). What type of mutation is this, and what is its likely effect?

Accepted Answer

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

Question 8

During translation, which molecule brings amino acids to the ribosome, and how does it recognize the correct codon?

Accepted Answer

tRNA; by its anticodon pairing with the mRNA codon.

Question 9

Which of the following best describes the difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

Eukaryotes have introns and exons in their genes, while prokaryotes typically do not.

Question 10

A gene undergoes a frameshift mutation due to the insertion of a single nucleotide. What is the most likely consequence?

Accepted Answer

All codons downstream of the mutation are altered, potentially resulting in a nonfunctional protein.

Question 11

Which formula correctly represents the calculation of the number of possible codons in the genetic code?

Accepted Answer

$$4 	imes 4 	imes 4 = 64$$

Question 12

In a Time of Entry Map experiment, which gene will be transferred first during conjugation between Hfr and F- strains?

Accepted Answer

The gene closest to the origin of transfer on the Hfr chromosome.

Question 13

Which of the following best describes the role of exconjugants in bacterial conjugation experiments?

Accepted Answer

Exconjugants are recipient cells that have received new genetic material via conjugation.

Question 14

Which mutation type is most likely to result in a gain of function phenotype?

Accepted Answer

Missense mutation that increases protein activity.

Question 15

During a cross between two bacterial strains, you observe that the genotype of the recipient includes genes from both donor and recipient. What is this phenomenon called?

Accepted Answer

Partial diploidy (merodiploidy).

Question 16

Which equation would you use to calculate the number of possible polypeptides from a gene with $$n$$ codons, assuming no stop codons?

Accepted Answer

$$20^n$$

Question 17

A bacterial colony grows on selective media only if it has received a gene for antibiotic resistance. What does this indicate about the genotype of the colony?

Accepted Answer

The colony is an exconjugant and has incorporated the resistance gene.

Question 18

Which of the following is a real-world example of a suppressor mutation?

Accepted Answer

A second mutation restores the function lost by a previous mutation, such as a tRNA mutation that allows read-through of a stop codon.

Question 19

Which process is responsible for the formation of partial diploids (merodiploids) in bacteria?

Accepted Answer

Conjugation involving F' plasmids.

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