(a)(i) Explain the term co-ordinance. (ii) Calculate the number of individuals with co-dominant blood group. (iii) What is the total number of individuals i...

(a)(i) Co-dominance

Co-dominance is a condition in which both alleles of a gene are fully and equally expressed in a heterozygous individual. Neither allele masks the other. For example, \(I^A\) and \(I^B\) are co-dominant alleles; hence \(I^AI^B\) produces blood group AB.

Survey calculations

(a)(ii) The co-dominant blood group is AB.

\[\frac{32.8}{100}\times250=82\]

Therefore, 82 individuals have the co-dominant blood group.

(a)(iii) A person with blood group B can receive blood from persons with blood groups B and O.

\[\text{Number with group B}=\frac{14.0}{100}\times250=35\]

\[\text{Number with group O}=\frac{45.2}{100}\times250=113\]

\[35+113=148\]

Therefore, 148 individuals can donate blood to the accident victim with blood group B.

(b) Genetic diagram

Heterozygous blood group A man: \(I^Ai\)
Blood group AB woman: \(I^AI^B\)

Gametes from the man are \(I^A\) and \(i\), while gametes from the woman are \(I^A\) and \(I^B\).

The possible genotypes and phenotypes of the children are:

• \(I^AI^A\): blood group A
• \(I^Ai\): blood group A
• \(I^AI^B\): blood group AB
• \(I^Bi\): blood group B

Thus, the possible blood groups are A, AB and B, in the ratio:

\[2\text{ A}:1\text{ AB}:1\text{ B}\]

That is, 50% blood group A, 25% blood group AB and 25% blood group B. No child will have blood group O.