(a) In a family of four individuals, the father possessed long ears and the mother possessed short ears. If the parents had pure dominant and recessive traits respectively and F1 individual is married to an unrelated individual of the same genotype, then calculate the ratio of genetic makeup of F2 generation. Show a suitable cross.

(b) If father had short ears and the mother had long ears, and both the parents are homozygous for the allelic pair of genes, explain what effect it will have on the ratio of genetic makeup in F2 generation, if F1 individual is married to an unrelated individual of the same genotype.

(a) Let L = long ears (dominant), l = short ears (recessive).

Father (pure dominant) = LL; Mother (pure recessive) = ll.

P : LL × ll

F1 : all Ll (long)

F1 individual marries an unrelated individual of same genotype → Ll × Ll

F2 :

F2 genotypic ratio: 1 LL : 2 Ll : 1 ll (Phenotype: 3 long : 1 short)

(b) Father short = ll, Mother long = LL (both homozygous).

P : ll × LL → F1 : all Ll (long), same as in (a).

Again Ll × Ll → F2 genotypic ratio: 1 LL : 2 Ll : 1 ll (phenotype 3 : 1).

Effect : No change in the F2 generation and the ratio will still be same i.e., 1 LL : 2 Ll : 1 ll because the cross is still between a pure dominant and recessive allele as shown in the cross above.