Question 1

Which experiment provided definitive evidence that DNA, and not protein, is the genetic material in bacteriophages?

Accepted Answer

Hershey and Chase's experiment using $$^{35}S$$ and $$^{32}P$$ labeled T2 phages

Question 2

In eukaryotic transcription, which post-transcriptional modification is essential for mRNA stability and export from the nucleus?

Accepted Answer

Addition of a 5' 7-methylguanosine cap

Question 3

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

Accepted Answer

Nonsense mutation

Question 4

Which of the following best describes rolling circle replication?

Accepted Answer

Replication of circular plasmids in prokaryotes, producing multiple copies

Question 5

In the lac operon, what happens when lactose is present and glucose is absent?

Accepted Answer

The operon is activated, and transcription occurs

Question 6

Which formula is used to calculate the distance between two mutations in T4 rII mapping, and why is it multiplied by 2?

Accepted Answer

Distance $$= \left( \frac{\#WT\ (Restrictive)}{Total\ (Permissive)} ight) 	imes 100 	imes 2$$; multiplied by 2 because recombination can occur in either direction

Question 7

Which of the following is a real-life example of a chromosomal deletion leading to a human condition?

Accepted Answer

Cri-du-Chat syndrome

Question 8

A eukaryotic gene can produce multiple protein isoforms from a single mRNA transcript. Which mechanism allows this?

Accepted Answer

Alternative splicing

Question 9

Which statement correctly describes the difference between prokaryotic and eukaryotic promoters?

Accepted Answer

Prokaryotic RNA polymerase binds directly to the promoter, while eukaryotic RNA polymerase requires transcription factors

Question 10

Which of the following best explains why only one gene can be translated from an mRNA in eukaryotes?

Accepted Answer

The presence of the Kozak sequence ensures translation starts at a single site

Question 11

Which type of mutation is most likely to result in a conditional lethal phenotype?

Accepted Answer

A mutation that is only lethal under certain environmental conditions

Question 12

In a Mendelian dihybrid cross between two true-breeding parents (AaBb x AaBb), what is the expected phenotypic ratio in the offspring?

Accepted Answer

$$9:3:3:1$$

Question 13

Which mechanism is responsible for the movement of genetic elements within the genome, potentially causing mutations?

Accepted Answer

Transposition

Question 14

Which of the following is an example of aneuploidy?

Accepted Answer

A human cell with 45 chromosomes (monosomy)

Question 15

In bacterial Hfr mapping, what is the significance of the time at which a gene is transferred during conjugation?

Accepted Answer

It indicates the relative position of the gene on the chromosome

Question 16

Which of the following best describes co-dominance in genetics?

Accepted Answer

Both alleles are fully expressed in the phenotype

Question 17

Which process is primarily responsible for genetic recombination in bacteria?

Accepted Answer

Homologous recombination mediated by RecA protein

Question 18

Which of the following is a real-world example of sex determination that differs from humans?

Accepted Answer

Birds use a ZW system, where females are ZW and males are ZZ

Question 19

Which of the following best describes epistasis?

Accepted Answer

One gene masks or modifies the expression of another gene

Comprehensive Genetics Study Notes: DNA, Gene Expression, Mutations, and Mapping

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