Question
Generally it is observed that human males suffer from hemophilia more than human females, who rarely suffer from it. Explain giving reasons. or F₁ progeny of pea plant bearing violet flowers and snapdragon plant bearing red flowers were selfed to produce their respective F₂ progeny. Compare the phenotypes, the genotypes and the pattern of inheritance of their respective F₂ progeny.
Answer :
This is a sex linked / X chromosomes linked recessive disease ,the heterozygous female / carrier for hemophilia may transmit the disease to sons (male progeny), The possibility of hemophilic female/daughter is rare because mother of such a female has to be at least carrier and the father should be hemophilic.
or
The red colour in the snapdragon flower shows incomplete dominance if crossed with white colour flower the genotype Rr is pink colour in it. So they will have RR as genotype.
When self-pollination:
R R
R RR RR Genotype 4:0, phenotype all red
R RR RR
Violet genotype is Rr, violet is a dominant trait. When selfed in F2 generation
R r
R RR rR Genotype ratio 1:2:1, phenotype 3:1 (3 violet, 1 white)
r Rr rr
The pattern of inheritance is complete dominance. The dominant allele is expressed and the recessive allele is suppressed in both the case. The phenotype is of the dominant allele.
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