MODULE 6
OCR A
MANIPULATING
GENOMES
BIOLOGY
___
Notes
2% of genome = coding exons
Non-coding DNA:
- Satellite DNA= short sequences repeated many times in same positions in chromosome,
but the number of repeats varies btw individuals b/C different length of repeats
inherited from both parents
- Minisatellite: sequence of 20~50 base pairs repeated 50~100 times at 1000 locations
(VNTRs)
- Microsatellite: 2-4 base pairs repeated 5~15 times (STRs)
DNA PROFILING
1. Extract DNA and cut it into small fragments using restriction endonucleases at specific
nucleotide sequences / restriction sites
→2 cuts (1 through each strand) not within the satellites so remain intact
2. Separate fragments through gel electrophoresis
- Insert them into wells at 1 end
- Gel immersed in buffer solution
- Electric current: DNA is negatively charged due to the PO₄³- so is attracted to the anode
- Gel: mesh resists movement
- Smallest fragments move fastest as they experience less friction from the gel
, - When the other end is reached: power is switched off
- Gel in alkaline buffer solution to denature fragments and separate strands
- Southern bloating : strands in nylon membrane over gel and covered with sheets of dry
absorbent paper
- Drawing alkaline solution through membrane by capillary action to transfer fragments
to the membrane in precisely the same positions as they were on the gel (since they
can’t pass through it )
- Radiograph film: visible pattern of light and dark bands unique and highly specific
DNA probes : sequence of bases complementary to DNA
Locate the gene
,
OCR A
MANIPULATING
GENOMES
BIOLOGY
___
Notes
2% of genome = coding exons
Non-coding DNA:
- Satellite DNA= short sequences repeated many times in same positions in chromosome,
but the number of repeats varies btw individuals b/C different length of repeats
inherited from both parents
- Minisatellite: sequence of 20~50 base pairs repeated 50~100 times at 1000 locations
(VNTRs)
- Microsatellite: 2-4 base pairs repeated 5~15 times (STRs)
DNA PROFILING
1. Extract DNA and cut it into small fragments using restriction endonucleases at specific
nucleotide sequences / restriction sites
→2 cuts (1 through each strand) not within the satellites so remain intact
2. Separate fragments through gel electrophoresis
- Insert them into wells at 1 end
- Gel immersed in buffer solution
- Electric current: DNA is negatively charged due to the PO₄³- so is attracted to the anode
- Gel: mesh resists movement
- Smallest fragments move fastest as they experience less friction from the gel
, - When the other end is reached: power is switched off
- Gel in alkaline buffer solution to denature fragments and separate strands
- Southern bloating : strands in nylon membrane over gel and covered with sheets of dry
absorbent paper
- Drawing alkaline solution through membrane by capillary action to transfer fragments
to the membrane in precisely the same positions as they were on the gel (since they
can’t pass through it )
- Radiograph film: visible pattern of light and dark bands unique and highly specific
DNA probes : sequence of bases complementary to DNA
Locate the gene
,
