#detecting variation

Variation can be at the phenotypic level through to the molecular level.

look for visible differences in the phenotype

chromosome differences eg., length of long arm of Y

immunological markers eg., blood groups

protein gel electrophoresis eg., esterases in Drosophila

SSLPs (Simple sequence length polymorphisms) or VNTR (variable number of tandem repeats)

STR or (short tandem repeats)

Single nucleotide polymorphisms (SNP)

Discontinuous Variation

mid digital hair present or absent

blue or green budgerigar

black or brown dog

Variable regions often in non-coding regions

Minisatellites 15 -100b (eg., tandem repeat of 18 bases) total length from 1-5kb.

Microsatellite short tandem repeats (STR): 2 - 9 bases – can have several alleles according to how many repeats

Single nucleotide polymorphism (SNP) 1 base – can only have two alleles at a locus

VNTR (variable number of tandem repeats)  Minisatellites

In non coding regions of the genome

Repeat sequence between 15bp -100bp long

But number of repeats varies from person to person so VNTR can be from 1 - 20kbs in length

Multilocus probe (found in more than one location)

–  minisatellites –  eg., tandem repeat of 18 bases total length from 1-5kb.

Single locus probe – minisatellites (as above) – microsatellite - short tandem repeats (STR) - 2 - 4 bases

Application Identification

Paternity

Forensic analysis – Crime