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How can the genome of an individual be said to be unique?
- Each person's genome contains many repetitive, non coding base sequences that are found in introns and between genes
- Each individual has a unique number and length of these sequences (other than MZ twins)
- The more closely related people are, the more similar their sequences
Describe stage 1 of genetic fingerprinting
DNA is extracted from the sample and amplified using PCR
Describe stage 2 of genetic fingerprinting
- DNA is cut into fragments using restriction endonucleases
- The endonucleases are chosen to have recognition sequences that are not part of the repeating sequence of interest
Describe stage 3 of genetic fingerprinting
The fragments are separated via gel electrophoresis
Describe stage 4 of genetic fingerprinting
The gel is washed in alkali to make the DNA single stranded to allow the probe to bind
Describe stage 5 of genetic fingerprinting
Radioactive probes, containing sequences complementary to the repetitive sequence of interest are added and allowed to hybridise
Describe stage 6 of genetic fingerprinting
X ray film is laid across the gel and the positions of the fragments are revealed as dark bands
How might forensic scientists use genetic fingerprinting?
- The patterns of bands allows DNA from different sources to be compared
- DNA from a crime scene can be compared with that of a suspect
How might genetic fingerprinting be used for medical diagnosis?
- Some repetitive non coding base sequences are linked to genetic diseases such as huntingtons
- The more of these repeats the person possesses, the more likely they are to suffer from the disease
- The longer the sequence of repeats, the larger the fragment which will show up as a band on the gel
How might plant and animal breeders use genetic fingerprinting?
- To establish how closely two organisms are related
- This is useful for avoiding inbreeding