DNA Replication Flashcards
what direction is DNA synthesised
DNA (+RNA) is always synthesised in the 5’ –> 3’ direction
- the parental strand goes 5’–> 3’
how many bonds does A-T have, and C-G
A-T = 2 C-G = 3
what are the 7 stages that is needed to make a DNA copy
- Progressive addition of new nucleotides
- a starting point for nucleotide addition
- unwinding of the helical double-stranded DNA
- release of tension generated by Unwinding the DNA helix
- Prevention of unwound double-stranded helical DNA
- Joining ends of newly synthesized fragments together
- removes RNA primer and fills gave with DNA nucleotides
which enzyme is used to add new nucleotides
- DNA Polymerase 3
which enzyme is used to make RNA primers
Primase enzyme
which enzyme is used to unwind the DNA
Helicase
which enzyme is used to nick and rejoin the DNA strand to release tension
Topoisomerase
which protein prevents the DNA strand to wind back up
Single stranded DNA binding proteins (SSD)
what enzyme is used to join the ends of the newly synthesised strands
DNA ligase
which enzyme is used to remove RNA primers and fill the gaps
DNA polymerase 1
what is the leading strand and the lagging strand
leading strand = continuously synthesised in it 5’ –> 3’ direction
lagging strand = discontinuously synthesised in its 5’ –>3’ direction as okazaki fragments
what are the 7 proteins/enzymes that help with DNA replication
- helicase
- topoisomerase
- Ssbp (single stranded DNA binding proteins)
- primase
- DNA polymerase 3
- DNA polymerase 1
- Ligase
describe the job of the enzyme Helicase
- it pulls the DNA strands apart
describe the job of the enzyme topoisomerase
- moves ahead of the replication fork and cuts both strands which allows them to unwind completely/release the tension.
- then glues the 2 strands back together
describe the job of the protein Ssbp
- when the DNA strands are apart, they bind to the single strands of DNA, which prevents the DNA going back together.
- they prevent the single strands of DNA from being degraded
describe the job the enzyme Primase does
- has catalytic properties
- has 3prime hydroxyl group that it uses to ass a short stretch of RNA nucleotides
describe the job the enzyme DNA polymerase 3 does
- It utilize the 3prime hydroxyl of the RNA primer and adds a DNA nucleotide to it.
- Adds 1 nucleotide at a time
- keeps extending the strand and kicks the Ssbp off when continuing the strand
describe the job the enzyme of DNA polymerase 1 do
- it recognizes the RNA and DNA hybrid, it then removes the RNA component
- it then uses the 3 prime hydroxyl group in the Okazaki fragment that is next door to it, and it extends the okazaki fragments up to the other fragments
- this it moves along to the other RNA
- IT DOES NOT CONNECT THE OKAZAKI FRAGMENTS TOGETHER
describe the job the enzyme Ligase does
- utilizes the 3 prime hydroxyl group that’s at the end of 1 fragment and the 5’ prime phosphate f the next door group/fragment and created a phosphors difate bond between the 2 fragments/nucleotides
- in the end you will have a continuous DNA strand
when can DNA errors be repaired
- during = EXOnuclease
- after = ENDOnuclease
describe what exonuclease are
are enzymes that cleave DNA sequences in a polynucleotide chain from other the 5’ or 3’ end. Only one at a time
describe what endonuclease is
a group of enzymes that cleave the phosphodiester bond present within a polynucleotide chain
what are the differences between endo and exonuclease
- exonuclease only take the incorrect nucleotide out of the DNA strand
- endonuclease takes a bulk of nucleotides and the incorrect one out of the DNA strand
what is PCR
the Polymerase chain reaction
what happens in the vitro method
- makes multiple DNA copies so that there is enough DNA material to work with
