Yes, two O positive parents can have a negative baby.
This is possible because blood type is determined by two genes, one inherited from each parent. While the O positive parents each carry two O alleles, they could also carry a recessive negative allele. If each parent passes on their negative allele, their child will inherit the O negative blood type.
Here's a breakdown:
- Blood type inheritance: Blood type is determined by the ABO and Rh genes.
- ABO gene: There are three alleles: A, B, and O. O is recessive, meaning it only expresses if both alleles are O.
- Rh gene: There are two alleles: positive (dominant) and negative (recessive).
- O positive parents: Can have the following genotypes:
- OO+ + (both parents have two positive alleles)
- OO+ - (one parent has one positive and one negative allele)
- O negative child: This is possible if both parents carry the negative Rh allele (OO+ -).
Example:
- Mother: OO+ - (O positive with one positive and one negative Rh allele)
- Father: OO+ - (O positive with one positive and one negative Rh allele)
- Child: OO- (O negative)
In summary, while two O positive parents typically have O positive children, they can also have an O negative child if they both carry the recessive negative Rh allele.
