Blood Types Tutorial

The Human ABO markers: The A, B, and O alleles

Introduction

Human ABO markers

Blood types and genotypes?

How are ABO alleles inherited by our children?


Blood type & Rh factor calculator

Blood type calculator

Rh factor

Problem set
Human blood type is determined by co-dominant alleles. An allele is one of several different forms of genetic information that is present in our DNA at a specific location on a specific chromosome.
Blood Types

There are three different alleles for human blood type:

Blood types For simplicity,
we call these
IA A
IB B
i O
Genotypes
Each of us has two ABO blood type alleles, because we each inherit one blood type allele from our biological mother and one from our biological father. A description of the pair of alleles in our DNA is called the genotype.

Since there are three different alleles, there are a total of six different genotypes at the human ABO genetic locus.

Allele from
Parent 1
Allele from
Parent 2
Genotype of
offspring
Blood types of
offspring
A A AA A
A B AB* AB
A O AO A
B A AB* AB
B B BB B
B O BO B
O O OO O


The Biology Project
University of Arizona
Thursday, October 23, 1997
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