Multiple Allele Crosses - ABO Blood Groups

OCR A-level BiologyGenetics and VariationLesson 40 of 41

ABO blood groups are controlled by one gene with three alleles: I^A and I^B are codominant, and both are dominant to I^O. The genotypes and phenotypes are:

• Group A: I^AI^A or I^AI^O
• Group B: I^BI^B or I^BI^O
• Group AB: I^AI^B
• Group O: I^OI^O

Worked example: a heterozygous group A father and a heterozygous group B mother have children.

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Key terms in this lesson

codominance: A type of inheritance in which two different alleles of a gene are both expressed in the phenotype of a heterozygote, rather than one masking the other.

Multiple Allele Crosses - ABO Blood Groups

Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz

Key terms in this lesson

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