Patient's question:
I am type O blood. I heard that children born to O-type blood parents have poor constitutions. My daughter is one of those who are very frail. I also heard that if you have a child with an AB-type man, the child might not survive. Is there any truth to this?Doctor's answer:
Chromosomes on somatic cells are called homozygous if the alleles from both parents are the same (e.g., alleles A and A on some A-type chromosomes): if the gene content is different, they are called heterozygous (e.g., in some A-type human chromosomes, the alleles are A and O). In other words, every individual has two and only two alleles at a specific locus, with each allele coming from one parent. If the alleles from both parents are the same, the individual is called homozygous; if they are different, the individual is called heterozygous. Whether homozygous or heterozygous, the sum of genes on a pair of chromosomes is called the genotype. As mentioned above, the genotypes of the two types of individuals are AA and AO, respectively. However, not all inherited genes are expressed. The traits that can be expressed are called the phenotype. For example, whether the genotype is AA or AO, the phenotype is A, which is what we commonly refer to as type A. It is clear that blood type actually refers to its phenotype. The difference between the phenotype and the genotype is that some genes can express their traits whether they are homozygous or heterozygous. Such genes are called dominant genes. If the traits controlled by such genes are only expressed in homozygotes and not in heterozygotes, these genes are called recessive genes. In the ABO blood group system, the A and B genes are dominant, while the O gene is recessive. For example, in a pair of chromosomes, one carries the A gene and the other carries the O gene. The genotype of this person is AO, but the phenotype is A, meaning type A, not type O. Type O individuals have O genes on both chromosomes.