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DNA replication
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1
Question
What are the three models of DNA replication?
Answer
Conservative, semi-conservative, dispersive
2
Question
Which experiment proved semi-conservative replication?
Answer
Meselson and Stahl (E. coli in 15N then 14N)
3
Question
What enzyme unwinds the DNA helix?
Answer
Helicase
4
Question
What prevents overwinding of DNA ahead of the fork?
Answer
Topoisomerase
5
Question
Which proteins keep DNA strands apart?
Answer
Single-strand binding proteins (SSBs)
6
Question
Which enzyme makes the RNA primer?
Answer
Primase
7
Question
Which enzyme extends the DNA strand from the primer?
Answer
DNA polymerase III
8
Question
Which enzyme replaces RNA primers with DNA?
Answer
DNA polymerase I
9
Question
Which enzyme joins Okazaki fragments?
Answer
DNA ligase
10
Question
Why are leading and lagging strands different?
Answer
DNA polymerase only adds to 3' end; leading is continuous, lagging is discontinuous (Okazaki fragments)
11
Question
How does DNA polymerase correct errors?
Answer
Proofreading activity (exonuclease function)
12
Question
What is mismatch repair?
Answer
System removing incorrectly paired bases after replication
13
Question
What is nucleotide excision repair?
Answer
Removes thymine dimers caused by UV damage
14
Question
Why does replication shorten chromosomes?
Answer
Lagging strand cannot be fully copied; telomeres shorten with each replication
15
Question
What is telomerase?
Answer
Ribonucleoprotein enzyme with RNA template; reverse transcriptase to extend telomeres
16
Question
What is the three models of DNA replication?
Answer
Conservative, semi-conservative, and dispersive models of replication
17
Question
Which experiment demonstrated semi-conservative replication?
Answer
Meselson–Stahl experiment using 15N and 14N in E. coli
18
Question
What unwinds the DNA double helix?
Answer
Helicase catalyzes strand separation