Question

Seed color in radishes is determined by a single gene. Radish seeds come in three colors: purple, brown and orange. A gardener plants all purple seeds in his isolated garden and collects the resulting seeds produced. 157 purple, 73 brown and 81 orange seeds were collected. What type of inheritance does this represent? What is the most probable genotype of each parent? Based on your answer above, what genotypic and phenotypic ratios are expected in these progeny?

Answer 1

Answer

The Probable cross is represented as follows :

Assume BB for brown colour, bb for orange colour. Then Bb for purple colour

The farmer planted purple seeds and assume that they are self pollinated. then,

Parents - Purple seed x Purple seed

Genotype - Bb x Bb

Gametes - B and b x B and b

Progeny -

  

Gametes	B	b
B	BB Brown	Bb Purple
b	Bb Purple	bb Orange

1. The type of inheritance is Incomplete dominance. In Incomplete dominance, one allele of a trait is not completely dominant over the other allele. The heterozygous condition produce a third phenotype. This third phenotype is a blend of the two alleles.

2. The Probable genotype of the parents is - Bb and Bb

3. Phenotypic ratio - 1 : 2 : 1 ( 1 Brown : 2 Purple : 1 Orange )

Genotypic ratio - 1 : 2 : 1 ( 1 BB : 2 Bb : 1 bb )