Recombinant Technology Flashcards
What are DNA probes
Short single-stranded pieces of DNA
- Base sequence is complementary to bases on part of a target disease
- Usually labeled with fluorescent or radioactive with a fluorescent or radioactive tag so can be identified
Why are probes longer than just a few bases
- A sequence of a few bases would occur in many places throughout the genome.
- Longer sequences only likely to occur in the target allele
What is DNA hybridisation
Binding of single-stranded DNA probe to complementary single strand of DNA forming hydrogen bonds
Name the process of locating specific alleles of a gene
- Extract DNA and amplify using PCR
- Use Restriction enzymes to cut DNA at a specific base sequence
- Separate DNA fragments by gel electrophoresis according to length.
- Transfer to a nylon membrane and treat to form single strands with exposed bases.
- Labelled DNA probe will hybridise with its target allele ( then wash to remove the unbound probe)
- To show probe is bound to either :
expose membrane to UV light if fluorescently labelled probe used
- Use autoradiography ( expose to X-ray film ) if radioactive probe used
State 3 advantages of using a DNA probe
- Screening patients for heritable conditions e.g. cystic fibrosis > find out if a carrier
- Screening patients for drug responses
- Screening for health risks e.g. alleles that predispose to breast cancer
alleles that predispose to high blood cholesterol
Explain what a genetic counsellor does
- Explain the results of the screening
- Discuss treatments available for the genetic condition
- Discuss lifestyle choices/ precautions that might reduce the risk of a genetic condition developing e.g. a mastectomy
- Explain the probability of condition/alleles being passed on to offspring > enable patients to make an informed decision about having children
For genetic screening
Can enable people to make lifestyle choices to reduce choices of disease developing
Choose whether to have their own biological children
Against genetic screening
Screening for incurable disease or ones that develops later in life nothing positive can be done may lead to depression
Could lead to discrimination by insurance companies
May cause undue stress if never goes on to develop disease
What are VNTRs
Repeating sequences of nucleotides found with non-coding sections of DNA of many sites throughout the genome
What do VNTRs allow
Allow the production of a virtually unique genetic fingerprint
- Probability of 2 individuals having the same VNTRs is very low
Because the genomes organisms contain many VNTRs and length differ between individuals
Technique of VNTRs
- Amplification
- Extract DNA from a sample e.g. blood
Amplify by the PCR - Digestion
Use RE to cut DNA into smaller fragments
Which cut at specific sites near VNTRs leaving VNTR intact - Separation
Separate DNA/VNTRs using gel electrophoresis according to length shorter VNTRs travel further - Hybridisation
- Transfer from gel to the nylon membrane
Treat DNA to separate strands ( make single traned) ( add alkaline)
Technique of VNTRs
- Amplification
- Extract DNA from a sample e.g. blood
Amplify by the PCR - Digestion
Use RE to cut DNA into smaller fragments
Which cut at specific sites near VNTRs leaving VNTR intact - Separation
Separate DNA/VNTRs using gel electrophoresis according to length shorter VNTRs travel further - Hybridisation
- Transfer from gel to the nylon membrane
Treat DNA to separate strands ( make single stranded) ( add alkaline)
Apply DNA probes complementary to VNTRs with a radioactive / fluorescent label - Development
Use autoradiography or use UV light to visualise banding patterns
Purpose of GE
separating nucleic acid ( DNA/RNA) fragments or proteins by size
Process GE
- load DNA samples into wells in porous of gel and cover in buffer solution ( conducts electricity)
- Pass electrical current through > DNA is neg charged so moves towards pos electrode
- Shorter DNA fragments travel faster so travel further
The use of genetic fingerprinting
More similar VNTRs > more similarities in genetic fingerprints
Paternity testing
Determining genetic variability within the population.
