a. HLA = Human leukocyte antigen, typing is a method to determine how closely the tissues of one person match the tissues of another person. Human leukocyte antigens are proteins you inherit from your parents. Together, your HLA proteins, or markers, make up your HLA type. We currently know of more than 2,500 different HLA markers.HLA typing is used to match donor and recipient for transplants e.g. tissue, bone marrow, kidney etc.
- The most likely place to find an HLA match between two people is among siblings who have the same mother and father.
b. DNA profiling looks at certain parts of the DNA called markers. Different markers are given different numbers to distinguish them from each other. Obligatory alleles are compared with that of parents, siblings, or close relatives for kinship analysis or can be used in forensics.
1. Two unrelated people can just happen to be a good HLA match, too. Although it is less likely, it is possible that you could have some of the same HLA markers as someone you don’t even know.
- But you can not meet a stranger having same DNA profile as yours.
2. If you have brothers or sisters, there is a 25% chance that you will have inherited the same six HLA as one of them, a 50% chance of having three of the same antigens and a 25% chance of having none of the same antigens.
- Even though siblings share half their DNA, they can share any number of markers in a DNA test.
Interesting cases: Tetragametic chimera – a mixture of two individuals, formed by the fusion of two zygotes in the womb which grows as a single individual. It can lead to a false interpretation in the analysis of stain material in crime cases and in paternity testing because a mixed pattern of different genotypes can be obtained in one individual.
Monozygotic twins – Monozygotic twins are derived from the zygote of one sperm and an ovum which splits into two or more zygotes. Such twins cannot be differentiated with the conventional DNA typing methodologies and a case involving them can lead to false inclusion.