Chapter 15 DNA Synthesis and Repair Flashcards
semiconservative replication
parental strand separate and each serves as a template for a new daughter strand
conservative replication
the bases of both strands temporarily turned out from the nucleus, allowing for both strands to be copied, resulting in a completely identical double helix that is identical to the parent
dispersive replicastion
parental double helix was cut at regular intervals and synthesize in short sections then the daughter strands would be a mix of old and new DNA segments.
origin of replication
where the initial replication bubble forms
replication fork
Y shaped region where the parental DNA is separated into single strands and copied
DNA helicase
opens the double helix by breaking the hydrogen bonds between the base pairs
DNA primase
synthesizes the RNA primer
Single Strand DNA binding proteins
stabilize the single strand to prevents them from snapping back into a double helix
topoisomerase
cuts and unwinds the double helix to relieve the twisting forces during replication
DNA polymerase
synthesizes leading strand in the 5’ to 3’ direction
sliding clamp
hold DNA polymerase in place during strand extension
purpose of the RNA primer in DNA replication
DNA polymerase only works in the 5’ to 3’ direction but needs a 3’ end to extend from, RNA strand about 12 base pairs long will form to complement a strand with an OH at the end for the polymerase to bind to
primase
a type of RNA polymerase that synthesizes the RNA primer
discontinuous replication hypothesis
the DNA polyermase can only synthesize bases in the 5’ to 3’ direction, so primase synthesizes primers to which polymerase can connect too
DNA ligase
catalyzes the formation of phosphodiester bonds between fragments, essentially forming the phosphate backbone and sealing up the double helices.
replisome
a macromolecular machine made up of the proteins involved in replication
telomere
the region at the end of the eukaryotic chromosome
why is it difficult to replicate the end of a chromosome
somatic cells are unable to use the final RNA primer to replicate the end of the lagging strand
telomersase
an enzyme that carries a sequence of the same repeating bases and attached to the overhanging section of unreplicated DNA. and allows polymerase to synthesize to the end of the DNA, keeping the telomeres from shortening.
why do basticerial cells not need telomerase?
the chromosome in bacteria are a circle, there is to “end” that a primer falls short of and there is onely 1 replication point
how does polymerase correct for mistakes
polymerase can proof read and remove mismatched pairs because they have a recodnizable shape
nucleotide excision repair
used to remove damaged DNA, like the thymine dimers the result from UV light exposure
