DNA Analysis - VNTRs

repeat sequences in DNA

portions of DNA contain sequences of nucleotides/bases that are repeated numerous times

these sections of the DNA do not code for proteins and their origin + significance is unknown

the number of tandem repeat sequences

differ from one individual to another and means its possible to distinguish between individuals

VNTRs

variable number tandem repeats

these are examined using RFLP

repeat sequences don’t code for proteins and seem to be filler DNA between genes

they are inherited from our parents in the same way all DNA is

all humans have same types of repeats

but there is a huge variation in the number of repeats at different regions of the genome

a core sequence is 15-100 bases long and repeats itself up to 1000 times

restrictive enzymes

repeats are cut out of the DNA using enzymes

restriction fragments

the cut pieces of DNA through the use of restriction enzymes

polymorphic

the fragments vary in length and are therefore referred to as polymoric

RFLP

restriction fragment length polymorphism

RFLP analysis

this process involves DNA isolation, restriction, electrophoresis and probing

once the DNA is cut into fragments they are separated out on a gel subjected to an electric field

DNA is chemically treated so the strands are separated

DNA is then transferred to a nylon membrane by a process called southern blotting

to detect fragments containing the repeats, the membrane is treated with small (radioactive or chemiluminescent) DNA fragments called probes which bind to the repeat sequences

those fragments containing repeat sequences are visualised by exposing the membrane to an X ray film