DNA Replication

what direction is dna synthesized in

5’ to 3’ direction

semi-conservative process

where one strand of dna serves as a template for a new complementary strand of dna

helicase

enzyme that unwind dna at origins of replications and creates replication forks

topolomerase

straightens the dna strands by breaking, swiveling, and rejoining dna strands after coming out of helicase

primase

puts down rna primer to start replication

dna polymerase

adds complementary bases to leading strand

what direction does dna polymerase add bases

new dna is made from 5’ to 3’

lagging strand

the strand that is growing from 3’ to 5’ direction

how does the lagging strand grow

by using Okazaki fragments

how does leading strand grow

by dna polymerase

leading strand

the strand that is grow from 5’ to 3’

okazaki fragments

short segments of dna that are built on lagging strand

how does lagging strand work

addition of lagging strand allows for dna polymerse to add from 5’ to 3’ (since lagging is 3’ to 5’)

dna polymerase II

replaces rna primer with dna

dna ligase

seals fragments together

statistics of pairing errors

1 in 100,000 nucleotides

statistics of complete dna errors

1 in 10 billion nucleotides

nucleases

enyzme that cut damaged dna; dna poly and ligase fill in the gaps

problem with many replications

dna strand will grow shorter as there is no way to complete 5’ ends of daughter strands

tolemere

repeated units of short nucleotide sequences (TTAGGG)

telomere purpose

caps ends of DNA to postpone erosion of genes

telmoerase

adds to telomeres