Biomedical Engineering Reference
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(indicated by letters of specific bases) given below. The periods represent
bases that do not vary between individuals, the letters represent bases that
do vary between some individuals (snPs), and the slashes mark the two
ends of the haploblock.
/ . . . A . . . . . . C . . T . . . . . . . . G . . T . . . /.
This particular pattern of snPs represents one haplotype of this particular
haploblock on chromosome 3. The same haploblock in a person from Japan
might look like this:
/ . . . G . . . . . . C . . T . . . . . . . . G . . C . . . /.
And the haploblock from most nigerians might look like this:
/ . . . G . . . . . . T . . C . . . . . . . . G . . C . . . /.
here we have three possible haplotypes for the haploblock on chromosome
3 that we are considering. notice that all five snPs occur at the same loca-
tions in all three haplotypes but that the identity patterns of the snPs dif-
fer between haplotypes. every disease-causing mutation is inherited along
with the snPs of the haplotype within which the mutation arose.
This is a wonderful thing for medical researchers. it is as if a disease-
causing mutation is a burglar wearing a red cap, green pants, orange shirt,
and purple gloves that he can never shed. if you find a person with that
combination of clothing, you have probably found the burglar. likewise, if
you find that everybody with a particular disease also carries a particular
haplotype, you know that the culprit gene is amongst those snPs, at a par-
ticular region on a particular chromosome. figure 5.1 illustrates the way
snPs and disease-causing genes hang together within haplotypes during
the DnA mixing that accompanies egg and sperm formation.
The hapmap Project mapped the locations of the several hundred thou-
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