DNA replication Flashcards
1
Q
what direction do polynucleotides run in
A
-opposite directions (antiparallel)
1
Q
what is the enzyme called that unzips DNA
A
helicase
2
Q
what is the enzyme breaking to separate the 2 strands
A
hydrogen bonds
3
Q
what is the role of polymerase
A
binds to the primer and makes new DNA bases, catalyses the addition of new nucleotide bases in the 5’ 3’ direction
4
Q
why can the logging strand not be made continuously
A
as it runs in the opposite direction
5
Q
why is replication referred to as semi-conservative
A
made up of one strand is from parental DNA and one strand is newly synthesised
6
Q
stages of dna replication
A
- DNA unwinds catalysed by the gyrase enzyme and hydrogen bonds between the bases are broken causing it to unzip catalysed by helicase
- free nucleotides in the nucleoplasm
- the free nucleotides pair up with their complementary base pair on the single strands DNA
- DNA polymerase catalyses the addition of the new nucleotide bases, in the 5’ to 3’ direction, to the single strand DNA. unzipped DNA used as a template
- The leading strand is synthesised continuously from 5’ to 3’, whereas the lagging strand is synthesised in fragments from 3’ to 5’. DNA polymerase will fall off and reattach a few bases later leaving a gap in the backbone. this is later joined by a ligase enzyme
- two new DNA molecules are formed by semi-conservative replication. each DNA molecule consists of one parent strand and a new strand
