What does homozygous or heterozygous mean?
Zygosity in humans refers to whether you carry two like alleles (homozygous) or two different alleles (heterozygous) for a gene. Parents with a suspected case of NAIT will undergo testing to determine their zygosity for several known platelet antigens to look for antigens where an incompatibility may result in the baby. The most common incompatibility is with the HPA-1 antigen where the mother is homozygous HPA-1b (two like HPA-1b alleles) and the father is either homozygous or heterozygous HPA-1a (i.e., HPA-1a/HPA-1a or HPA-1a/HPA-1b).
