Question 1

Which statement best describes the 'central dogma' of molecular biology?

Accepted Answer

Genetic information flows from DNA to RNA to protein.

Question 2

Which of the following is a structural difference between DNA and RNA?

Accepted Answer

DNA is usually double-stranded, while RNA is usually single-stranded.

Question 3

During DNA replication, which enzyme is responsible for relieving supercoiling ahead of the replication fork?

Accepted Answer

Gyrase

Question 4

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides in the 5' to 3' direction, so the lagging strand is synthesized discontinuously.

Question 5

In prokaryotic transcription, what is the role of RNA polymerase?

Accepted Answer

It synthesizes RNA from a DNA template.

Question 6

Which of the following statements correctly distinguishes between codons and anticodons?

Accepted Answer

Codons are three-nucleotide sequences on mRNA, while anticodons are complementary sequences on tRNA.

Question 7

Which of the following is a key difference between prokaryotic and eukaryotic protein synthesis?

Accepted Answer

In prokaryotes, transcription and translation can occur simultaneously, while in eukaryotes they are separated by the nuclear envelope.

Question 8

Given the mRNA sequence 5'-AUG GCU UAA-3', which amino acids are encoded? (Use a standard codon table.)

Accepted Answer

Methionine - Alanine - Stop

Question 9

Which of the following best describes an inducible operon?

Accepted Answer

It is usually off but can be turned on in the presence of a specific substrate.

Question 10

Which microbe uses reverse transcription, and what is the process?

Accepted Answer

HIV; converting RNA to DNA

Question 11

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

Accepted Answer

Nonsense mutation

Question 12

How does UV light cause mutations in DNA?

Accepted Answer

By inducing the formation of thymine dimers, which disrupt normal base pairing.

Question 13

What is the purpose of the Ames test?

Accepted Answer

To assess the mutagenic potential of chemical compounds.

Question 14

Which process describes the direct transfer of DNA from one bacterium to another via a pilus?

Accepted Answer

Conjugation

Question 15

In Griffith’s experiment with S. pneumoniae, what did the transformation of rough (R) strain bacteria by heat-killed smooth (S) strain demonstrate?

Accepted Answer

Bacteria can acquire genetic material from their environment.

Question 16

Which of the following best describes a plasmid?

Accepted Answer

A small, circular piece of DNA that replicates independently of the bacterial chromosome.

Question 17

Which of the following statements about simple staining is correct?

Accepted Answer

Simple staining uses a single stain to visualize cell shape and arrangement.

Question 18

Which of the following is the correct order of solutions used in the Gram stain procedure?

Accepted Answer

Crystal violet, iodine, alcohol, safranin

Question 19

What is the main structural difference in the cell walls of Gram-positive and Gram-negative bacteria that leads to different Gram stain results?

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.

Question 20

Which bacterial arrangement describes spherical cells in clusters?

Accepted Answer

Staphylococcus

Genetics and Microbial Staining: Study Guide for Microbiology Module 3

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