DNA Profiling/Fingerprinting
Principles:
Uses non-coding DNA (doesn’t code for proteins) because all humans have SAME
GENES (Coding DNA)
Alleles = genes (base sequence) that have mutated (changed) bring about variation.
Uses repetitive sequences in non-coding DNA which vary in number of repeat
sequences (length of DNA fragment) in each individual
GEL ELECTROPHORESIS separates these DNA fragments by length.
Each individual had unique DNA barcode (except identical twins)
Each person has non-coding DNA in known LOCI that contains repeated DNA
sequence
Number of repeats of sequence varies between each person for each locus
*CAGTCACAGTCACAGTCA* = variable number tandem repeats (VNTR’s)
Short repeat *CATCATCAT* = Short Tandem Repeats (STR’s)
Number of repeats in sequence (VNTR’s/STR’s) makes length different
Each person carries 2 alleles of each of these repeat sequences because they get 1
allele from mum + 1 from dad. (if present on locus of 1 chromosome; will be at the
same locus on homologous chromosome.
VNTR/STR’s cut using restriction endonucleases
Enzymes - Cut DNA at specific base sequences
Mixture of VNTR/STRs can be separated by length + charge by gel electrophoresis
(chromatography)
DNA = Acid so gives away H+ and leaves DNA molecule to be negative
Use electricity to separate DNA segments of different lengths, those negative strands
go to positive electrode
Results in DNA fingerprint
Shorter DNA fragments = move faster than long ones
EXAM SPEAK METHOD
Uses VNTR/STRs – regions of non-coding with variable base sequence repeats
Principles:
Uses non-coding DNA (doesn’t code for proteins) because all humans have SAME
GENES (Coding DNA)
Alleles = genes (base sequence) that have mutated (changed) bring about variation.
Uses repetitive sequences in non-coding DNA which vary in number of repeat
sequences (length of DNA fragment) in each individual
GEL ELECTROPHORESIS separates these DNA fragments by length.
Each individual had unique DNA barcode (except identical twins)
Each person has non-coding DNA in known LOCI that contains repeated DNA
sequence
Number of repeats of sequence varies between each person for each locus
*CAGTCACAGTCACAGTCA* = variable number tandem repeats (VNTR’s)
Short repeat *CATCATCAT* = Short Tandem Repeats (STR’s)
Number of repeats in sequence (VNTR’s/STR’s) makes length different
Each person carries 2 alleles of each of these repeat sequences because they get 1
allele from mum + 1 from dad. (if present on locus of 1 chromosome; will be at the
same locus on homologous chromosome.
VNTR/STR’s cut using restriction endonucleases
Enzymes - Cut DNA at specific base sequences
Mixture of VNTR/STRs can be separated by length + charge by gel electrophoresis
(chromatography)
DNA = Acid so gives away H+ and leaves DNA molecule to be negative
Use electricity to separate DNA segments of different lengths, those negative strands
go to positive electrode
Results in DNA fingerprint
Shorter DNA fragments = move faster than long ones
EXAM SPEAK METHOD
Uses VNTR/STRs – regions of non-coding with variable base sequence repeats
