The following four crosses all apply to diploid organisms. Assume that all the p

Question

The following four crosses all apply to diploid organisms. Assume that all the parents are true breeding. You are given the phenotypes of the parental generation and the phenotypic ratio of the F2 generation. You must answer the following information: 1) genotypes of the parents 2) the phenotypic ratio expected for a testcross of the F1

Define your symbols.

a) P cross: Red x Brown

F2 Phenotype  Ratios:        

9 red-brown

3 red

3 brown                                  

1 white

1a) Parental Genotypes:

2a) Phenotypic ratio expected for a testcross of the F1 :

b) P cross: Red x Tall

F2 Phenotype  Ratios:        

     1 red, tall

2 red, intermediate

2 pink, tall

4 pink,intermediate

2 pink, short

1 white, tall

2 white, intermediate

1 white short

1b) Parental Genotypes:

2b) Phenotypic ratio expected for a testcross of the F1 :

c) P cross: albino 1 x albino 2

F2 Phenotype  Ratios:        

     9 wild type

7 albino

1c) Parental Genotypes:

2c) Phenotypic ratio expected for a testcross of the F1 :

Explanation / Answer

(a)

1a) the parental genotypes are: RRBB and rrbb

The F1 genotype is: RrBb

The cross is:

F2 Phenotype Ratio: 9 red-brown: 3 red: 3 brown: 1 white

2a) phenotypic ratio expected for a testcross of the F1 is 1: 1: 1: 1

(b)

1b) Parental Genotypes: RRTTand rrtt

The F1 genotype is: RrTt

The cross is:

2b) phenotypic ratio expected for a testcross of the F1: 1: 1: 1: 1

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