D1.1 DNA REPLICATION Flashcards
DNA Replication
The synthesis of an exact DNA copy with identical base sequence as original strand.
Why is DNA Replocation needed?
So that both daughter cells have the entire genome.
What 3 processes is cell division a part of?
- Growth
- replacement of damaged tissue.
- reproduction, providing cells that become gametes.
What is DNA described as?
Semi-conservative
why is DNA called Semi-conservative?
Each DNA molecule has one old strand and one new strand.
Why are the two strands of DNA identical to each other in base sequence?
Complementary base pairing.
Why is complementary base pairing important?
Ensures dna rep is accurate.
Replication fork:
site where a parent DNA molecule is separated into 2 single strands. §
Outline DNA replication in steps:
1) Helicase unwinds double helix and breaks H-bonds.
2) DNA polymerase links existing nucleotides to form new strands using the old one as a template strand.
3) New DNA molecule rewinds into double helix.
What is PCR used for?
DNA Amplification
where is PCR carried out in?
small tubes called eppendorfs.
What do Eppendorfs contain? (state reasons)
- DNA sample
- Taq DNA Polymerase, heat-stable enzyme, allows higher temps to be used.
- Primers: short DNA fragments that bind to DNA sample§s after being split by heat.
- DNA nucleotides for assembling new strands.
How many primers are needed?
2
Outline the temp change cycle of PCR
1) DNA heated to 95 to separate the 2 strands.
2) Temp reduced to 53, primers can bind to both strands next to desired sequence.
3) Temp increased 73 which encourages Taq DNA to replicate both strands starting at the primer.
DNA Amplification
There are twice as many copies of a desired DNA base sequence.
Gel Electrophoresis
Separating method for charged DNA fragments with different sizes.
Outline the procedure of Gel Electrophoresis:
1) A mixture of macromolecules is placed on a thin sheet of gel (mesh of inert material such as agarose).
2) Electrodes are attached at both ends.
3) DNA moves to the negative end because phosphate groups are negatively charged.
4) Small molecules move faster than large ones.
What are the uses of Gel Electrophoresis?
Separating DNA with short tandem repeats.
How are PCR and Gel Electrophoressi applied for DNA profiling:
1) DNA sample is taken
2) Primers are used to create to promote simultaneous amplification of 15 STRs by PCR.
3) STRs are separated by Gel electrophoresis.
What are applications of PCR and gel electrophoresis?
- Forensic investigations
- Paternity tests
In what direction does DNA replication occur:
DNA Polymerase III adds free nucleotides to the deoxyribose at the 3’ terminal (5 to 3)
The two DNA strands are…
ANTI-PARALELL
Compare Leading and Lagging Strands of DNA:
1) Leading Strand:
- replication is continuous
- RNE Primer Initiates once
- DNA polymerase moves towards the replication fork.
2) Lagging Strand
- DNA Polymerase III moves away from the replication fork.
- Short DNA fragments called Okazaki fragments are used to replicate the strand.
- discontinuous replication.
- RNA Primer Initiates several times
Helicase function
- unwinds double helix - separates strands
DNA Primase
Adds a RNA primer to dna strand
DNA Polymerase III Func (Lagging)
Binds to lagging strand at 3’ end of RNA primer + adds DNA nucleotide.
DNA Polymerase I
Removes RNA Primer and replaces it with DNA, leaves a gap.
DNA Ligase
Seals up the gap between okazaki fragments, makes sugar-phosphate bond
DNA Primase (Func - Leading)
Adds primer to 3’ to 5’ end, DNA polymerase can bind
DNA Polymerase III
Moves toward replication fork and adds free nucleotides to assemble DNA.
DNA Proofreading
DNA Polymerase III moves back to the mismatched pair, excises it and re-inserts a nucleotide with a correct base.
