Question 1

During DNA replication, which enzyme is responsible for unwinding the double helix and exposing the template strands?

Accepted Answer

Helicase

Question 2

Which of the following best describes the directionality of DNA polymerase III during DNA replication?

Accepted Answer

It synthesizes DNA in the 5' to 3' direction only.

Question 3

A mutation causes DNA ligase to become nonfunctional. Which of the following would most likely occur during DNA replication?

Accepted Answer

Okazaki fragments on the lagging strand would not be joined together.

Question 4

Which base pairing is correct according to the rules of DNA structure?

Accepted Answer

Adenine pairs with Thymine

Question 5

During the S phase of the cell cycle, DNA replication occurs. If a cell starts with $2 	imes 10^9$ base pairs, how many base pairs will be present after replication is complete?

Accepted Answer

$4 	imes 10^9$

Question 6

Which of the following statements about the lagging strand during DNA replication is correct?

Accepted Answer

It is synthesized discontinuously in short fragments called Okazaki fragments.

Question 7

Which type of RNA carries the genetic code from the nucleus to the ribosome for protein synthesis?

Accepted Answer

mRNA

Question 8

A DNA segment has the sequence 5'-ATG CCG TAA-3'. What would be the sequence of the mRNA transcribed from this DNA?

Accepted Answer

5'-UAC GGC AUU-3'

Question 9

Which of the following best describes the role of tRNA during translation?

Accepted Answer

It brings specific amino acids to the ribosome based on codon-anticodon pairing.

Question 10

A patient has a mutation in the gene encoding RNA polymerase. Which process would be directly affected?

Accepted Answer

Transcription

Question 11

If a DNA template strand has the sequence 3'-TAC GGA CTT-5', what is the corresponding mRNA sequence produced during transcription?

Accepted Answer

5'-AUG CCU GAA-3'

Question 12

Which of the following best explains why the genetic code is described as a 'triplet code'?

Accepted Answer

Each amino acid is coded by a sequence of three nucleotides (codon).

Question 13

During protein synthesis, which of the following events occurs at the ribosome?

Accepted Answer

Translation of mRNA into a polypeptide chain

Question 14

A scientist is studying a cell in which the RNA primer is not replaced by DNA. Which enzyme is most likely defective in this cell?

Accepted Answer

DNA polymerase III

Question 15

Which of the following best describes the relationship between a gene and a polypeptide?

Accepted Answer

A gene is a segment of DNA that carries instructions for a polypeptide chain.

Question 16

Which of the following is a correct sequence of events in the central dogma of molecular biology?

Accepted Answer

Transcription → Translation

Question 17

A mutation changes a codon in mRNA from UAU to UAA. What is the likely effect on the resulting protein?

Accepted Answer

The protein will be prematurely terminated because UAA is a stop codon.

Question 18

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

Accepted Answer

Each new DNA molecule consists of one old (parental) strand and one new strand.

Question 19

A patient is diagnosed with a disorder that affects ribosomal RNA (rRNA) production. Which cellular process would be most directly impaired?

Accepted Answer

Protein synthesis at the ribosome

Question 20

If a DNA strand has the sequence 5'-GCT ACG TTA-3', what is the complementary DNA strand sequence?

Accepted Answer

3'-CGA TGC AAT-5'

DNA Replication and Protein Synthesis: Structure and Function in Human Cells

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