Question 1

Which of the following best describes the structure of DNA?

Accepted Answer

DNA is a double-stranded helix with a sugar-phosphate backbone and nitrogenous bases paired by hydrogen bonds.

Question 2

During DNA replication, which enzyme is responsible for unwinding the double helix?

Accepted Answer

DNA helicase

Question 3

If a DNA strand has the sequence 5'-CAGGAAGCATA-3', what is the sequence of the newly synthesized complementary strand?

Accepted Answer

3'-GTCCTTCGTAT-5'

Question 4

Which of the following statements about genome size and organism complexity is correct?

Accepted Answer

There is no relationship between genome size and complexity.

Question 5

What is the main difference between DNA and RNA?

Accepted Answer

DNA contains deoxyribose sugar, while RNA contains ribose sugar.

Question 6

Which of the following is the correct sequence of events in gene expression?

Accepted Answer

Transcription → Translation → Protein folding

Question 7

A mutation changes a single nucleotide in a gene. Which type of mutation is this?

Accepted Answer

Point mutation

Question 8

Which of the following best explains why the genetic code uses three nucleotides per codon?

Accepted Answer

Three nucleotides allow for coding of 64 possible amino acids, covering all 20 amino acids.

Question 9

Which enzyme is responsible for joining Okazaki fragments during DNA replication?

Accepted Answer

DNA ligase

Question 10

In E. coli’s lac operon, lactose binds to a __________ protein, which prevents it from binding to the operon’s __________, thereby allowing RNA polymerase binding to the __________ to transcribe the lactose-digesting genes.

Accepted Answer

repressor; operator; promoter

Question 11

Which of the following is least likely to cause a mistranslated protein?

Accepted Answer

Substitution

Question 12

If a missense mutation occurs in a start codon, what is the most likely outcome?

Accepted Answer

Translation will not initiate, and the protein will not be produced.

Question 13

Which of the following is a real-world example of gene regulation in prokaryotes?

Accepted Answer

The lac operon in E. coli controlling lactose digestion.

Question 14

Which of the following statements about alleles is correct?

Accepted Answer

Alleles are different versions of a gene for the same trait.

Question 15

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

Each new DNA molecule consists of one old strand and one new strand.

Question 16

Which of the following is a correct application of complementary base pairing during transcription?

Accepted Answer

If the DNA sequence is 3'-TACGCTATC-5', the mRNA sequence will be 5'-AUGCGAUAG-3'.

Question 17

Which of the following is a function of tRNA during translation?

Accepted Answer

tRNA matches its anticodon to the mRNA codon and brings the correct amino acid.

Question 18

Which of the following is a plausible consequence of a point mutation in a gene?

Accepted Answer

It can result in a change in the protein’s amino acid sequence.

Question 19

Which of the following is true about the percentage of DNA that codes for protein in humans?

Accepted Answer

About 2% of human DNA codes for protein.

DNA Structure, Replication, Gene Expression, Regulation, and Mutation

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