DNA Flashcards
(15 cards)
1
Q
key features of DNA
A
- double stranded helix
- right handed helix
- antiparallel
- strands held together by complimentary base pairing
- outer edge of bases hold major and minor grooves
2
Q
antiparallel strands
A
- direction determined by sugar phosphate bonds
- phosphate groups connect 3’C of one sugar and another 5’C
- one strand has a free 3’C-3’ end
- one strand has a free 5’C-5’ end
3
Q
grooves
A
- backbones are closer together on one side - minor groove
- further apart on the other side - major groove
4
Q
double helix structure
A
- essential
- store huge volumes of energy
- precise replication in cell division
- nucleotide sequence determine sequence of amino acids - proteins determine phenotypes
5
Q
stages of DNA repair
A
- proofreading
- mismatch repair
- excision repair
- homologous recombination
6
Q
proofreading
A
- DNA polymerase recognises mismatched pairs, removes incorrectly paired bases
- catches 99% or more mismatches
7
Q
mismatch repair
A
- newly replicated DNA is scanned for mistakes by other proteins
- mismatches can be corrected
8
Q
excision repair
A
- scan DNA for damaged bases
- bases excised and DNA polymerase 1 adds the correct ones
9
Q
homologous recombination
A
- breaks in DNA can be repaired by copying from sister chromosome
10
Q
PCR
A
- Polymerase chain reaction
- automated process makes multiple copies of short DNA sequences for genetic multiplication and research
11
Q
PCR mixture consists of
A
- sample of double stranded DNA
- two artificially synthesised primers
- four dNTPs
- DNA polymerase
- salts & pH buffer
12
Q
stages of PCR
A
1) denature
2) annealing
3) extension
4) repeat
13
Q
PCR - denature stage
A
- heat mixture to 95oC
- strands melt apart and separate
14
Q
PCR - annealing stage
A
- cool mixture to 55oC
- huge concentration of primers bind to template
15
Q
PCR - extension stage
A
- heat mixture to 72oC
- new strand synthesised
