Biology [3 marks Question Answer]

Genotype - 1TTRR : 2TTRr : 2TtRR : 1ttRR : 4TtRr : 1TTrr : 2Ttrr : 2ttRR : ttrr
Phenotype - 9 - Tall and Round seeds ; 3 - Tall and wrinkled seeds; 3 - Dwarf and round seeds; 1 - Dwarf and wrinkled seeds.

Genotype - Tt
Phenotype - All tall

Genotype - TT : Tt will be 2:2 or 1:1
Phenotype - All tall plants

In F1 generation , all progeny produced will be hybrids Bb but will have black hair .

Importance of Mendel's Laws:
(i) Dominant and recessive characters can be found.
(ii) A hybrid with desired characters can be produced easily.
(iii) Crops can be improved.
(iv) Pure recessive characters can be used where needed.
(v) Genotypes and phenotypes of next generation can be predicted even before cross is made.

Cause of Haemophilia - Haemophilia is an X-linked inherited disease. Homozygosity for recessive haemophilia gene is must to be seen in a female while a single affected X chromosome makes the male a haemophilia victim.
Cause of Colour Blindness - Colour blindness is the effect of a recessive gene. In case of female, both the X chromosomes must have the recessive gene but as males have only one X chromosome, just a single affected chromosome causes colour blindness.