Rentas

VNTR

The full genetic profiles of any two individuals (other than
identical twins) reveal many differences. But since most human
genes are thesame from person to person, DNA typing relies on
the stretches of DNA that tend to differ among different people.
While the repeated sequencesthemselves are usually the same
from person to person, the number of times they are repeated
tends to vary.

The number of repeats can be gauged bydividing the entire
molecular weight of a given VNTR by the molecular weight of the
repeated sequence. VNTRs are similar to Short Tandem Repeats
(Formore on STRs, see page 3), the difference being that in a
VNTR, the repeated sequence is longer — about 10-100 base pairs
long.

These stretches ofrepeats, known as Variable Number of Tandem
Repeats or VNTRs, can be isolated from an individual’s DNA.

Tandem Repeats
Chromosome

Allele atLocus X

Repeat sequence
AT G C C

AT G C C AT G C C AT G C C AT G C C

AT G C C AT G C C

AT G C C

C
AT G C

C
AT G

C

C
AT GC

C
AT G

TGCC
CA

12 repeats
AT G C C

ating code
repe
onN

AT G C C AT G C C

AT G C C

C
AT G C

ting code
-repea
Non

5repeats

Variable Number
of Tandem Repeats (VNTR)
AGTTCGCGTGA AGTTCGCGTGA AGTTCGCGTGA AGTTCGCGTGA AGTTCGCGTGA

Repeat sequence length:
10-100base pairs/repeat
Short Tandem Repeats (STR)
AT G C C AT G C C AT G C C AT G C C AT G C C

Repeat sequence length:
2-9 base pairs/repeat