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Transcript of DNA profiling
blood, saliva, and semen all contain
cells with DNA in their nuclei DNA can also be extracted from
tissues 99.9% DNA in everyone is identical DNA profiling
or DNA fingerprinting The first method for creating a DNA profile was restriction fragment length polymorphism RFLP .
PCR Polymerase Chain Reaction
is usually the first step in the creation of a DNA profile today.
PCR is the first step in analyzing STRs (Short Tandem Repeats), which are very small, specific alleles in a variable number tandem repeat (VNTR).
Alleles are pairs of genes that occur alternately at a specific point, or loci, on a chromosome. If there is a match between two DNA fingerprints at eleven standard points, or loci, then the probability of the two DNA samples having come from different people would be 1 in 1 000 000 000 000 people differ on average 1 out of 1000 base pair (bp) some differences are in genes which lead to the visible differences between us some however are in "junk" DNA (that is not transcribed in RNA) within these regions there are short nucleotide regions known as Variable Number Tandem Repeats VNTR that are repeated in tandem several times CATCAT the number of copies of each sequence vary sensibly in different alleles in the same individual as one copy of the allele will come from one of the parents because of the great variability in VNTR for each allele if one examines enough different VNTRs (6 to 12) in a given person one can put together a DNA profile these DNA profiles can be used for identification of tissue left at the crime scene or for paternity testing in which case the VNTR alleles in the child which are not present in the mother must have come from the biological father is used to create
that can be used as evidence in a court case
by verifying the presence of VNTR sequences How does
technique work ? Quick Quiz What is junk DNA ?
Sketch a flow diagram showing the steps involved in DNA profiling.
What is the function of the restriction enzymes do? DNA is extracted
the sample DNA is cut with restriction enzymes, restriction endonuclease to produce specific fragments The fragments are separated according to size using the gel electrophoresis technique The DNA smear is transferred to a nylon membrane Labelled sequences of single stranded DNA called probes are added
the probes target the VNTR sequences i.e. the probe with the sequence GTA will bind with the sequence....? by