DNA replication Flashcards
why does DNA replication happen?
DNA has to be copy for a cell to divide. with out DNA replication cells could not divide, and you would die.
when does DNA replication occur?
DNA is copied during the S or synthesis phase of interphase
where does DNA replication start?
Replication starts at the origin of replication
Two strands open forming replication forks (y-shaped region)
what way does DNA Polymerase go?
DNA polymerase can only go in the 3’ to 5’ direction (this is why the lagging strand exists)
what is the first step of DNA replication?
the enzyme helicase separates the DNA into two strands by breaking the hydrogenbonds.
what is the second step of DNA replication?
the enzyme topoisomerases holds the DNA from coiling back up and keeps them in two forks.
what is the third step of DNA replication?
before new DNA strands can be name, primase puts down RNA primers to prepare for new nucleotides
what is the fourth step of DNA replication?
DNA polymerase goes from the 5’ to 3’ on the leading strand and places nucleotides
what is the fifth step of DNA replication?
DNA polymerase goes in the opposite direction of the strand (3’ to 5’) and makes fragments called okazaki fragments
what is the sixth step of DNA replication?
Ligase joins the okazaki fragments together
what is the seventh step of DNA replication?
proofreading enzymes check for mistakes. if there are any, DNA polymerase comes back and puts the right nucleotide.
what is the semiconservative model of replication?
an Idea presented by watson & crick where the two strands of the parental molecule separate, and each act as a template for a new complementary strand
New DNA consists of 1 parental and 1 new strand of DNA
what is Excision repair?
when any of over 50 repair enzymes remove damaged parts of DNA
what the enzymes in order of use in DNA replication?
Helicase
Topoisomerase
Primase
DNA polymerase
Ligase
Proofreading enzymes (a lot of them)
why is the lagging strand lagging?
as DNA continues to uncoil, DNA polymerase is still going from 3’ to 5’, but that strand goes from 5’ to 3’, so there to be another primer placed and DNA polymerase has to go and put more nucleotides.
