dna analysis - classical genetic marker (VNTRS)

repeat sequence in dna

portions of dna contain sequences of nucleotides that are repeated numerous times, these section do not code for proteins and their orgin and significance is unknown, the number of tandem repeat sequences differ from one individual to another and distinguish between individuals, are called variable number tandem repeats

VNTRS

variable number tandem repeats

restriction fragments

the repeats are cut out of the dna using restriction enzymes, the cut pieces are called restriction fragments, vary in length and referred to as polymorphic, this type of dna typing is called restriction fragment length polymorphism analysis ( RFLP )

RFPL

load fragment dna onto an agcrose gel, separates dna based on size, apply electric current - dna migrate positive terminal, one fragment has VNTR, transfer dna to nylon membrane, probes bind to repeat sequences for VNTR sequence, overlay membrane of gel - imprint from gel to membrane - southern blotting, fragments with repeat sequences are visualised by exposing the membrane to the x-ray film