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HLA Genetics (2) Usually a full brother or sister is the best chance
for an HLA match. Recall that each parent passes down only one of his/her
pair of number 6 chromosomes to each child. Most people carry a different
pair of alleles for the three major genes on each of their two number
6 chromosomes. Therefore, each chromosome 6 tends to carry a unique set
of particular HLA alleles. So for any given couple, there are 4 possible
combinations that can be inherited by each of their children. In the case
of a match, each sibling inherits the same chromosome 6 from mother and
the same chromosome 6 from father. Therefore, there is a 1 in 4, or 25%,
chance that a sibling will be a match for a child in need of a transplant.
Alternately, there is a 75% chance for a mismatch. If a related donor/recipient
match us not found, a search may be requested to identify an HLA-matched
donor through an unrelated bone marrow bank, such as the National Marrow
Donor Program. Because there are so many different alleles for each HLA
gene, the chance of finding an unrelated match is much less, although
it is more common among certain ethnic groups whose HLA types show less
variation. <next> |
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