Assignment: using punnett squares exploration

first cross: show a cross between a homozygous red bull (rr) and a heterozygous red cow (rr).

genotypic ratio:
phenotypic ratio:

second cross: show a cross between a heterozygous red bull (rr) and a heterozygous red cow (rr).

genotypic ratio:
phenotypic ratio:

third cross: show a cross between a homozygous white bull (rr) and a homozygous white cow (rr).

genotypic ratio:
phenotypic ratio:

Case I

Genotypic Ratio – RR: Rr = 2: 2 = 1: 1

Phenotypic Ratio – All the offspring are red in color as R is dominant over r

Case II

Genotypic Ratio – RR: Rr: rr = 1: 2: 1

Phenotypic Ratio – All RR and Rr are red in color while rr is of different color, thus the phenotypic ratio is Red offspring : White offspring = 3:1

Case III

Genotypic Ratio – All  offspring’s are of genotpe rr

Phenotypic Ratio – All offsprings are of white color

Explanation:

Case I – Homozygous red bull (RR) and a heterozygous red cow (Rr)

(R ) is dominant over ( r )  

The punnet square for the cross between the Homozygous red bull (RR) and heterozygous red cow (Rr) is as follows -  

RR

RRRRR

rRrRr

Genotypic Ratio – RR: Rr = 2: 2 = 1: 1

Phenotypic Ratio – All the offspring are red in color as R is dominant over r

Case II - heterozygous red bull (Rr) and a heterozygous red cow (Rr)

The punnet square for the cross between the heterozygous red bull (Rr) and a heterozygous red cow (Rr) is as follows -  

Rr

RRRRr

rRrrr

Genotypic Ratio – RR: Rr: rr = 1: 2: 1

Phenotypic Ratio – All RR and Rr are red in color while rr is of different color, thus the phenotypic ratio is Red offspring : White offspring = 3:1

Case III - homozygous white bull (rr) and a homozygous white cow (rr)

The punnet square for the cross between the homozygous white bull (rr) and a homozygous white cow (rr)  is as follows -  

rr

rrrrr

rrrrr

Genotypic Ratio – All  offspring’s are of genotpe rr

Phenotypic Ratio – All offsprings are of white color