(a) A child belongs to blood group 0 and the mother be-longs to group B. With the aid of genetic cross, state the possible blood groups of the father. (b) (...

Answer Details

(a) Genetic cross to find the father's blood group

The child is blood group O, so the child's genotype is ioio (recessive alleles only). The child must receive one io allele from each parent.

The mother is group B. She has passed an io to the O child, so her genotype must be Ibio (heterozygous B).

The father must also supply an io allele to the child. Any father whose genotype contains an io allele can do this. Therefore the possible genotypes of the father are:

• IAio (blood group A)
• Ibio (blood group B)
• ioio (blood group O)

A simple cross for a group O father shows this:

Mother (Ibio) × Father (ioio)

This gives group O children, confirming the father can be group O. The same reasoning shows he could also be group A (IAio) or group B (Ibio), because each of these carries an io allele. He cannot be group AB, because AB (IAIb) has no io allele to give an O child.

Possible blood groups of the father: A, B or O.

(b)(i) Two forms of adaptive communication in animals

Chemical communication (release of pheromones/scents) and sound/vocal communication (calls, songs). (Others: visual/display communication, tactile/touch communication.)

(b)(ii) Two reasons why organisms communicate

• To attract a mate for reproduction (courtship).
• To warn others of danger or the approach of an enemy.
• To mark and defend territory, or to indicate the source of food.