DNA REPLICATION

Question 1

why is DNA replication important

Answer 1

DNA is replicated prior to cell division so each daughter cell has a copy of the DNA Strand. → a full set of chromosomes.

Question 2

when does it occur

Answer 2

synthesis phase of the cell cycle

Question 3

state the 4 main enzymes involved

Answer 3

DNA helicase
DNA polymerase
DNA primase
DNA ligase

Question 4

what does DNA helicase do

Answer 4

It breaks the hydrogen bonds between base pairs, opening a section of DNA - the original strand.

Question 5

what is a replication fork

Answer 5

Y shape of DNA formed by helicase while it breaks the hydrogen bond between the strands of DNA

Question 6

what is the full name and purpose of SSB

Answer 6

single strand binding proteins

stabilises the strand while it is being unzipped

Question 7

what does DNA primase do

Answer 7

makes/adds RNA primer to the strands acting as a start point for the DNA polymerase.

Question 8

what does DNA polymerase do

Answer 8

DNA Polymerase attaches nucleotides to the leading strand from 5’ to 3’ forming a complementary strand. (following replication fork)

It also double checks errors and replaces the RNA primers with bases after the new strands are sealed.

Question 9

leading strand

Answer 9

continuous replication of DNA it is already 5’ to 3’

Question 10

lagging strand

Answer 10

Okazaki fragments are formed due to the strand being 3’ to 5’ and polymerase replicates 5’-3’

(moves away from replication fork constantly filling in sections.)

Question 11

what are Okazaki fragments

Answer 11

discontinuous segments of DNA on the lagging strand due to the carbon prime order.

Question 12

what does DNA ligase do

Answer 12

DNA Ligase joins the Okazaki fragments.

Question 13

why is DNA replication semi conservative

Answer 13

There is one ‘old’ strand- the original, parent strand - and a ‘new’ the daughter strand.