genetic dominace - codominace and blood typing

What is codominance?

A type of inheritance where both alleles are fully expressed in the phenotype with no blending.

How is codominance different from incomplete dominance?

In codominance, both traits are fully expressed; in incomplete dominance, traits blend.

Which alleles determine human blood type?

IA, IB, and i

What does the IA allele code for?

The production of A antigens on red blood cells.

What does the IB allele code for?

The production of B antigens on red blood cells.

What does the i allele code for?

No antigens on red blood cells.

Which blood type shows codominance?

Blood type AB, where both A and B antigens are present.

What is the genotype for blood type AB?

IAIB

What are the possible genotypes for blood type A?

IAIA or IAi

What are the possible genotypes for blood type B?

IBIB or IBi

What is the genotype for blood type O?

ii

Which alleles are dominant over i?

Both IA and IB

Why is blood type important in transfusions?

Receiving an incompatible blood type can cause coagulation and death.

What does the Rh factor (+ or -) indicate?

Whether the blood contains the Rhesus antigen (not required for this course).

Is IA dominant over IB?

No, IA and IB are codominant.

What happens if someone inherits IA and IB alleles?

They will have blood type AB with both antigens present.

What is the result of a person inheriting one IA and one IB allele?

They will have blood type AB.

Which allele is recessive in the ABO blood system?

i

What is the phenotype of a person with genotype IAi?

Blood type A

What is the phenotype of someone with IBIB genotype?

Blood type B

What is the phenotype of someone with ii genotype?

Blood type O

Why is blood type AB an example of codominance?

Because both A and B antigens are fully expressed.

If a person has blood type O, what alleles did they inherit?

i from both parents (ii)

Why must patients receive compatible blood during a transfusion?

Incompatible blood can coagulate and lead to death.

If a person has IAIB genotype, what antigens are present on their red blood cells?

Both A and B antigens

Can a person with IAIB genotype donate blood to someone with blood type A?

No, because their blood contains B antigens which type A cannot accept.

Table 1: Blood types and possible genotypes.

Figure 1: Blood type compatibility.