Replication and Transcription Flashcards
what problem of DNA replication does helicase fix?
exposing the template strand
helicase
moves down the DNA and separates strands using energy from ATP, uses single stranded binding proteins
single stranded binding proteins
prevent bases from rebinding to each other which creates the replication fork
how does helicase move?
helicase moves in both directions which makes a replication bubble and 2 replication forks
origin of replication
specific DNA sequence where helicases and polymerases start replication
how many origins of replication does a prokaryote have?
one
what problem does topoisomerase fix?
supercoiling
supercoiling
unwinding of helix shape creates overwinding which hinders transcription and replication
topoisomerase
cuts strands, allows them to unwind, and then rejoins the 2 sides
what problem does RNA polymerase fix?
DNA polymerase does not know where to start
RNA polymerase/primase
builds a short RNA primer so DNA polymerase can add DNA to the primer; DNA polymerase comes from other side and replaces primer
what direction is DNA replicated (built) in?
5’ to 3’ (starts at 3’ end of parent strand)
DNA ligase
joins together 2 replicated DNA fragments
why do leading and lagging strands occur?
helicase unwinds both strands 3’ to 5’ and 5’ to 3’ but DNA polymerase only elongates new strands 5’ to 3’
leading strands
leading strands are already going in the 5’ to 3’ direction of the new strand; replication chases helicase
