Unit Three- DNA Replication Flashcards
what is semi conservative replication
in new DNA there is one parental strand and one new strand
what are the three steps of DNA replication
-initiation
-elongation
-termination
what is the purpose of helicase
bind to the DNAat the origin and unravel the DNA ahead of the DNA fork
what is a single strand binding protein’s purpose
attach and keep the H bonds between the two separated pieces of DNA from reforming
what is the enzyme topoisomerase used for
it attaches to the fork to relive stress as it seperates
what enzymes catalyzes the addition of new DNA nucleotides (at what stage)
DNA polymerase 3
(elongation)
what is the first restrictions of DNA polymerase
-only add nucleotides in the 5’ to 3’ order
how does the first restriction of DNA polymerase effect replication in the lagging and leading strand
leading end-replication occurs continuously moving in the same direction as the replication fork
lagging strand- okazaki fragments (short nucleotide sequences) are syntheszed in the 5’ to 4’ direction
what splices okazaki fragments into place
the enzyme ligase
what is the second restriction of DNA polymerase
only adds nucleotides to existing nucleotide chains
-short strand of RNA is the primer (starting point) for each new DNA
other then RNA what enzyme creates the primer for new DNA strands
primase
how many primers does the leading and lagging strand require
leading-one
lagging- one for each okazaki fragment
what does DNA polymerase 1 do
chemically snipes out the primer and replaces it with DNA nucleotides
what are telomeres used for
at the end of each chromosomes, codes for useless segments, used as buffers to help prevent the loss of important genetic info
–> contain many guanine nucleotides
what is the last step of DNA replication
termination
-2 new daughter strands rewind to regain chem. stability
