Why is it possible that parents have Rh + blood and Rh children?
Whether we are "Rh positive" or "Rh negative" is determined by the presence or absence of a protein called D antigen on the surface of our erythrocytes (red blood cells), respectively. The RHD gene, located on the short arm of the first chromosome, is responsible for the formation of the D antigen protein. We have two copies of the first chromosome - one from our father and one from our mother. For the formation of a protein - D antigen, that is, for us to be "Rh +", we only need one functioning copy of the RHD gene (the so-called dominant inheritance). Thus, "Rh positive" are both people who inherit the first chromosome with a functioning copy of the RHD gene from both parents, and people who inherit the first chromosome with a functioning copy of the RHD gene from only one of the parents (white people from the other parent usually receive the first chromosome, which has no RHD gene at all, which is so-called deleted). It follows from the above that in a situation where each of the "Rh +" partners has a functional copy of the RHD gene only on one of the two chromosomes of the first pair, some of their children (25%) will inherit a chromosome without a functioning copy from both the father and the mother. of this gene that is, it will be "Rh-". It should be added that the maternal-fetal conflict occurs when a pregnant woman "Rh-" produces antibodies against the fetal D antigen "Rh +".
Remember that our expert's answer is informative and will not replace a visit to the doctor.
Krystyna SpodarKrystyna Spodar - specialist in the field of clinical genetics at NZOZ Genomed, ul. Ponczowa 12, 02-971 Warsaw, www.nzoz.genomed.pl, e-mail: [email protected]
The expert answers questions about genetic diseases and congenital malformations, inheritance, and prenatal diagnosis.
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