Both of my parents have rhD positive blood. I came out with rhD negative blood. How?

Question

Mum: O+
Dad: B+
Me: O-

In: 673

Answer 1

You get one copy of the rhD gene from your mom and one from your dad. The combination of those two genes results in your rhD expression.

The rhD+ gene is dominant, so if **either** of the two genes in the pair is +, then you will express as positive.

The genetic makeup of both of your parents is the same – they both have one gene that is positive and one that is negative. This results in them both expressing as rhD+.

They both passed to you their copy of the rhD- gene. Since both of your genes are rhD-, you express as rhD-

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Same thing with the blood types. A and B are dominant genes, while O is not. Your mum has two copies of the O gene, which means she expresses as O. Your dad has one copy of the B gene and one copy of the O gene, meaning he expresses as B. The both passed on to you an O gene, giving you two O genes, so you express as O just like your mum.