exam 3 - dna replication

central dogma of biology

describes how genetic information flows in a cell, DNA —> RNA —> proteins

prokaryotes

have single circular chromosome that is much smaller; 1 ORI

eukaryotes

have multiple chromosomes that are much larger; multiple ORIs

helicase

unzips the DNA helix at the replication fork by breaking the hydrogen bonds between strands

single-strand binding proteins

bind to and stabilize the single stranded templates; prevents DNA helix from rewinding

topoisomerase

releases tension by making single-stranded breaks to relieve supercoil strain

ligase

seals other nicks created during DNA replication (when primase is replaced with DNA, when Okazaki fragments are joined together)

DNA polymerase III (or δ and ε)

polymerase for regular synthesis

DNA polymerase II (or β)

polymerase for proofreading, repair/editing

primase

makes RNA primer

RNA primers

needed to initiate all new DNA strands; later removed by DNA polymerase

telomeres

short, repeating DNA sequences; present on DNA ends and added constantly to prevent loss of genes

telomerase

enzyme that adds telomeres; reverse transcriptase that uses an internal RNA template to extend 3’ end of linear chromosomes

parent strand

serves as a template; the DNA strand that is being unwinded

daughter strand

generated by complementary base pairing; has one old and one new strand

origin of replication

where proteins bind to and replication bubble created

functional restrictions of DNA polymerase

1. can only copy single-stranded DNA

2. can only add onto existing free end

3. can only add nucleotides onto -OH of a free 3’ end

DNA polymerase I (or δ)

polymerase for removing RNA primer and filling gap with DNA

DNA polymerase a

polymerase that works with primase to start replication

continuous synthesis

the leading strand has a ________ ________

discontinuous synthesis

the lagging strand has a ________ _________

leading strand

synthesized in the 5’ —> 3’ direction

lagging strand

synthesized in the 3’ —> 5’ direction

okazaki fragments

short segments of DNA synthesized on lagging strand; each fragment needs a separate primer