You breed Cactus Roses & you produce two pure breeding lines based upon petal sh

Question

You breed Cactus Roses & you produce two pure breeding lines based upon petal shape: Round
& Serrated. A single gene normally controls petal shape, i.e., there is 1 gene with 2 alleles (A &
a). When you cross your true breeding lines, all the progeny produced are Serrated (in shaped).
However, when you cross two F1’s to produce your F2, you find a new phenotype: Oblong (long
& narrow, which is not an intermediate phenotype). Your results for the F2 are as follows:
Serrated 357; Oblong 89; Round 27. A) Is this trait controlled by a single gene, why or why not?
B) If not, propose an explanation to explain these results? & C) Indicate the genotypes of the P &
F1 generation individuals?

Explanation / Answer

A) Is this trait controlled by a single gene, why or why not?

This trait is not controlled by single gene and is due gene interaction, epistasis

Two separate genes that coded for two separate characteristics in a dihybrid cross and the phenotypic ratio deviate from 9:3:3:1.

Epistasis is an interaction at the phenotypic level of organization

An allele at one locus mask the effect of the another allele

An allele at one locus modify the effect of another allele

Two or more loci interact to create new phenotype

C) Indicate the genotypes of the P & F1 generation individuals?

genotypes of the P

parent in the P generation produces gamete

Petal shape round = SsRr

F1 offspring produces two kinds of gamete

Ss X Rr

Self polination of F1 offspring produces

each Parent produces 4 different combinations of alleles in the gametes

SsRr = SR, Sr, rS, rs

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