1.11. DNA replication Flashcards
DNA stores ___ (___ ___) which are…
genes, genetic information, sections of DNA (on one strand only) with specific base sequence.
DNA polymerization always happens in ____ direction.
5’ to 3’
leading strand template
the original DNA strand which gets polymerized instantly as it unwinds - from down to up direction (5’ to 3’)
lagging strand template
the original DNA strand which gets polymerized in fragments - use Okazaki fragments in the process of polymerization
why is DNA replicated
to produce two identical copies of it and provide them to daughter cells in cell division
semi-conservative model of DNA replication
each of the two copies of the DNA contain one strand of the original DNA
the free-floating DNA/RNA nucleotides are found in ___ in prokaryotes and in ___ in eukaryotes.
nucleoid, nucleoplasm
prokaryote DNA
- circular/ring -shaped
- only one point of origin or replication (helicate attaches to only 1 point)
(P have only one chromosome and it’s small)
eukaryote DNA
- linear (has beginning and end)
- helicase attaches to multiple points - several origin points
(E have more and bigger chromosomes/longer DNA than P - speeding up the process)
replication fork
site until where helicase has split the parental DNA
DNA synthesis may occur…
…bi-directionally from the origin.
DNA polymerization is ___ by short RNA sequences that are called…
initiated/primed, RNA primers
why are RNA primers necessary
because DNA polymerize III can only join a nucleotide when there is an already existing, free 3’ end to attach it to and enzyme primase which attaches RNA (primase) does not have this limitation (more primitive)
unlike connected nucleotides, free-floating have…
3 phosphate groups - when they join with other nucleotides the 2 extra groups detach and by doing that provide energy for the formation of the phosphodiester bond (3’-5’ linkage)
free nucleotide with A N-base
free nucleotide with G N-base
free nucleotide with T N-base
free nucleotide with C N-base
together they are all called:
deoxyriboadenosine triphosphate
deoxyriboguanosine triphosphate
deoxyribotimosine triphosphate
deoxyribocytosine triphosphate
deoxyribonucleoside triphosphate
ATP (adenosine triphosphate) is free…
deoxyriboadenosine
how do ATP->ADP->AMP reactions release energy
by detaching their phosphate groups
deoxyribonucleoside triphosphate =
N-base + deoxyribose + 3PO^3-
other name for RNA nucleotides
ribonucleoside triphosphates
enzymes involved in DNA polymerization
- helicase
- primase
- DNA polymerize III
- DNA polymerize I
- gyrase
- ligase
- single-strand binding proteins
function of gyrase
also called topoisomerase - relieves the pressure from the super-condensed upper part of the DNA by unwinding the DNA from above (opposite direction from helicase)
function of single strand binding proteins
keeping the newly separated DNA strands from coming back together due to attraction forces between their complimentary N-bases
6 steps of DNA polymerization
1| helicase unzips and unwinds the existing DNA by breaking H-bonds between complimentary N-bases of the two strands
2| free RNA nucleotides in the nucleoplasm/nucleoid attach themselves to the now free N-bases on the separated DNA strands
3| primase connects the two RNA primers by creating a phosphodiester bond between them
4| DNA polymerize III attaches free DNA nucleotides to the next free N-bases and forms 3’-5’ linkages between DNA segments and bordering DNA and RNA nucleotides
5| DNA polymerize I digests the RNA primers
6| ligase creates phosphodiester bonds between the two separated parts of the new strand (fills in the gaps)
