(a) Explain the following terms:
(i) trait
(ii) recessive gene
(iii) test cross
(iv) heterozygous
(b) How do you determine whether a man with blood group ‘0’ and married to a woman with blood group ‘AB’ is the father of a child with blood group ‘AB’ born to them?
(c) (i) In rabbit brown hair is dominant over white hair colour. How could you determine that a brown coloured male rabbit is homozygous?
(ii) What is the difference between the chromosome number of a gamete and that of the body cell of the same organism?
Explanation
(a)(1) Trait: Characteristic of an organism controlled by pairs of genes.
(ii) Recessive gene: Member of a pair of genes in a genotype, whose characteristics are not manifest in the phenotype / in the presence of its contrasting gene / allele
(iii) Test cross: Mating / exposing of the heterozygous individual of Fl generation, to homozygous recessive parents
(iv) Heterozygous: This refers to the genotype, consisting of two different / contrasting genes / alleles
Blood group of Blood Blood Blood Blood
Offspring Group A Group B Group A Group A
No, the man cannot be-the father of the child.
(c)(i) Test cross: The male rabbit (Brown) is mated with a homozygous white female rabbit, having the recessive trait, f the male is homozygous all the offspring will be brown, if the male is heterozygous half of the offspring will be brown and half white.
(ii) Gamete and somatic chromosome number: The gametes contain half the number of chromosomes / n / haploid number of chromosomes, found in the body / somatic diploid / 2n cell.