Question

1. which enzyme is responsible for building a new dna strand by adding complementary bases?

a) helicase
b) ligase
c) dna polymerase
d) topoisomerase

1. a student claims that dna replication is conservative because one new molecule is entirely new dna. what is the error in this claim?

a) replication is actually dispersive.
b) replication produces rna, not dna.
c) replication is semiconservative; each new molecule has one old and one new strand.
d) replication happens in the cytoplasm, not the nucleus.

1. which situation would most likely require endonuclease activity instead of exonuclease activity?

a) removing a single incorrect base at the end of dna
b) repairing a mutation that occurs in the middle of a dna strand
c) adding primers to the lagging strand
d) unwinding dna ahead of the fork

1. a scientist mutates the helicase enzyme in a eukaryotic cell. which of the following outcomes is most likely?

a) okazaki fragments will not be joined correctly.
b) dna strands will not be separated for replication.
c) rna primers will not be placed.
d) the dna will not be proofread for errors.

Explanation:

Question 7

• Helicase unwinds DNA. Ligase joins DNA fragments. Topoisomerase relieves supercoiling. DNA Polymerase adds complementary bases to build new DNA strands.

• DNA replication is semiconservative (each new DNA has one old and one new strand), not conservative. Option A is wrong (replication is semiconservative, not dispersive in main model). Option B is wrong (replication produces DNA). Option D is wrong (replication is in nucleus for eukaryotes).

• Endonucleases cut within DNA, exonucleases cut at ends. Option A: end of DNA → exonuclease. Option B: middle of strand → endonuclease. Option C: primase adds primers, not endonuclease. Option D: helicase unwinds, not endonuclease.

Answer:

C) DNA Polymerase

Question 8