Final answer:
A woman with type O blood, which has a genotype of ii, can have a child with type A blood if the biological father has a genotype of IAIA or IAi, contributing an A allele. Since A and B are codominant and O is recessive, the child's phenotype for blood type will be determined by the dominance of the A or B allele inherited from the father.
Step-by-step explanation:
To understand how a woman with type O blood a child with type A blood can have, it's key to know the genetics of the ABO blood group system. Since the woman has type O blood, her genotype must be ii, meaning she possesses two recessive alleles. For her child to have type A blood, the child must inherit one A allele (IA) and one O allele (i) to be heterozygous (IAi), or two A alleles (IAIA) to be homozygous. This can only happen if the biological father contributes an A allele.
Considering A and B alleles are codominant, and O is the recessive allele, it is possible for the woman's child to have type A blood if the father’s genotype is either homozygous (IAIA) or heterozygous (IAi) for the A allele. The mother’s contribution will always be an O allele (i) since she has only recessive alleles. Therefore, the child can receive genotype IAi from the parents, resulting in type A blood.
Genotypes for blood type A are either IAIA (homozygous) or IAi (heterozygous), and for blood type O is ii (homozygous recessive). When a child inherits an A allele from a parent with type A blood and an O allele from a parent with O blood, the child will have type A blood due to the dominance of the A allele over the O allele.