Question

in a cross between your plant with violet flower and pure plant with white flower offspring of F1 progeny allha violet flower win the elephant rogini has self crossed it was observed in the F2 progeny that out of hundred seventy five flower are violet make a cross of two F2 progeny mention the genotype and phenotype of F1 progeny give one reason why in F1 progeny both the parental threat are not expressed​

Answer 1

Answer:

Consider the dominant allele to be represented by "V" and the recessive allele to be represented by "v".

• On crossing two F2 progenies, the following F3 progenies can be formed:

1. All Violet F3 progenies:

When a homozygous dominant (violet) F2 progeny is crossed with either a homozygous dominant (violet) or a heterozygous dominant (violet) or a homozygous recessive (white) F2 progeny.

    2. Half violet and half white F3 progenies:

When a heterozygous dominant (violet) F2 progeny is crossed with a homozygous recessive (white) F2 progeny.

     3. Three-fourth violet and one-fourth white F3 progenies:

When two heterozygous dominant (violet) F2 progenies are crossed with each other.

     4. All white F3 progenies:

When two homozygous recessive (white) F2 progenies are crossed with each other.

• The F1 progeny has a heterozygous dominant (Vv) genotype and violet phenotype.
• Both the parental traits (violet and white) are not expressed in the F1 progeny because the dominant violet colour trait masks the recessive white colour trait.

Explanation:

• An allele can be defined as two contrasting forms of the same gene.
• According to Mendel's Law of Dominance, of the two alleles of a gene, one is capable of expressing itself even when present in a single copy in a heterozygous individual. This is called the dominant allele. The other allele whose effect gets suppressed in presence of the dominant allele in a heterozygous individual but which can get expressed in a homozygous individual is called the recessive allele.
• The F1 progeny on self-crossing produces 75 violet flowers and 25 white flowers in the F2 generation. This is possible when the F1 progeny that was self-crossed had a heterozygous dominant (Vv) genotype and violet phenotype.