Topic 3 (replication)

Question 1

What is replication?

Answer 1

to produce exact copies of something

Question 2

DNA replication produces new DNA chains and…

Answer 2

exact copies of identical base sequences

Question 3

DNA replication is semi-conservative, why?

Answer 3

Because it contains 1 parental chain and one newly synthesized chain, an equal mix. Meanwhile, conservative synthesizes new helix, and dispersive make mixed fragments of parental DNA chains.

Question 4

What does the following mean: “DNA replication is semi-conservative”

Answer 4

That each of the two resulting daughter DNA molecules contain an original (parental) strand and a new synthesized strand.

Question 5

How can the following be proved: ““DNA replication is semi-conservative””

Answer 5

With the Mendelssohn-Stahl experiment

Question 6

State the three steps of replication

Answer 6

1. Separation and unwinding of DNA
2. Synthesis and attachment of primer
3. Elongation (synthesis of new strand)

Question 7

Explain the first step of replication.

Answer 7

First, gyrase (prokaryotes) or topoisomerase II (prokaryote and eukaryote) prepares the strand for uncoiling and relieves the strains in the double helix.
Helicase protein is attached to the strand, (helices is ring shaped), then it breaks the hydrogen bonds between the two strands. As a result we have the replication fork.

Question 8

Explain the second step of replication.

Answer 8

Primase is attached to a strand, then it produces a primer which is a strand of RNA which attaches to the DNA strand, that is later used as a base for elongation.

Question 9

Explain the third step of replication.

Answer 9

Primase detaches, then DNA polymerase attaches to DNA strand. After it starts to link nucleotides together to form the new strand of the DNA using the preexisting base pairs, creating an identical molecule to the parental one.

Question 10

Explain the third step of replication for the in the leading strand

Answer 10

Various DNA polymerase are attached to the strand as they only work 5’ to 3’. After they create their corresponding RNA fragments and start elongation up until the next DNA polymerase. This are Okazaki fragments.

Question 11

What is the leading strand

Answer 11

The strand which is below on the replication fork. (5 to 3) (Where okazaki fragments will be formed)

Question 12

What is DNA polymerase I and III

Answer 12

DNA polymerase I: replaces RNA with DNA in the gaps left by the primers during replication.
DNA polymerase III: elongation

Question 13

What is the result of replication?

Answer 13

Two newly synthesised strands that attach to the parental ones