Question 1

Which of the following best describes the flow of genetic information according to the Central Dogma of Biology?

Accepted Answer

DNA $$\rightarrow$$ RNA $$\rightarrow$$ Protein

Question 2

During DNA replication, which enzyme is responsible for unzipping the double helix by breaking hydrogen bonds between base pairs?

Accepted Answer

DNA helicase

Question 3

A scientist observes a mutation in a bacterial gene that changes a codon from UAU (tyrosine) to UAA. What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; introduces a premature stop codon

Question 4

Which of the following statements about the structure of DNA is correct?

Accepted Answer

The sugar in DNA is deoxyribose

Question 5

A bacterial cell is exposed to UV light, resulting in the formation of thymine dimers. Which enzyme can directly repair this damage using visible light?

Accepted Answer

Photolyase

Question 6

In the lac operon, what happens when lactose is present in the environment?

Accepted Answer

Lactose binds to the repressor, removing it from the operator and allowing transcription

Question 7

Which of the following best describes the difference between genotype and phenotype in bacteria?

Accepted Answer

Genotype is the DNA instructions; phenotype is the trait produced by those instructions

Question 8

A researcher introduces a plasmid carrying an antibiotic resistance gene into a bacterial population. After several generations, many bacteria express the resistance. Which gene transfer mechanism most likely occurred?

Accepted Answer

Conjugation

Question 9

During transcription, which of the following sequences correctly represents the direction in which RNA polymerase synthesizes the new RNA strand?

Accepted Answer

$$5' \rightarrow 3'$$

Question 10

A frameshift mutation occurs in a gene. Which of the following is the most likely consequence?

Accepted Answer

The reading frame is altered, potentially changing every amino acid downstream

Question 11

Which type of RNA is directly responsible for bringing amino acids to the ribosome during translation?

Accepted Answer

tRNA

Question 12

In the trp operon, what happens when tryptophan levels are high in the bacterial cell?

Accepted Answer

Tryptophan acts as a corepressor, enabling the repressor to bind the operator and block transcription

Question 13

Which of the following best explains why DNA replication is described as 'semi-conservative'?

Accepted Answer

Each new DNA molecule contains one original strand and one new strand

Question 14

A bacterial cell acquires a gene for antibiotic resistance from a virus that previously infected another bacterium. Which gene transfer process is this?

Accepted Answer

Transduction

Question 15

Which of the following codons serves as the universal start codon for translation?

Accepted Answer

AUG

Question 16

If a DNA sequence is $$5'	ext{-}ATGCGT	ext{-}3'$$, what is the complementary DNA strand?

Accepted Answer

$$3'	ext{-}TACGCA	ext{-}5'$$

Question 17

Which of the following best describes the function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments on the lagging strand

Question 18

A bacterial cell is able to take up naked DNA from its environment and incorporate it into its genome. This process is known as:

Accepted Answer

Transformation

Question 19

Which of the following statements about RNA is correct?

Accepted Answer

RNA uses uracil instead of thymine

Question 20

A mutation changes the DNA sequence from $$5'	ext{-}ATG	ext{-}3' to$$ $$5'	ext{-}ACG	ext{-}3'. $$The resulting protein has a serine instead of a methionine at the first position. What type of mutation is this?

Accepted Answer

Missense mutation

Microbial Genetics: The Central Dogma, Gene Expression, and Genetic Variation

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