Question

Questions 1. What conclusions can you draw about the results of your first cross, between a homozygous red bull (RR) and a heterozygous red cow (Rr)? Answer:


2. What conclusions can you draw about the results of your second cross, between a heterozygous red bull (Rr) and a heterozygous red cow (Rr)? Answer:


3. What conclusions can you draw about the results of your third cross, between a homozygous white bull (rr) and a homozygous white cow (rr)?

Answer 1

a)

$RR\:x\:Rr$
$\underbrace{RR\:x\:Rr}$
$RR, Rr, RR, Rr$
$\underbrace{RR,RR}_{50\%},\underbrace{Rr,Rr}_{50\%}$

Therefore:
Crossing results in 50% (dominant homozygote) and 50% (dominant heterozygote).

b)

$Rr\:x\:Rr$
$\underbrace{Rr\:x\:Rr}$
$RR, Rr, Rr, rr$
$\underbrace{RR}_{25\%},\underbrace{Rr,Rr}_{50\%}, \underbrace{rr}_{25\%}$

Therefore:
Crossing results in 25% (dominant homozygote), 50% (dominant heterozygote) and 25% (homozygous recessive).

c)

$rr\:x\:rr$
$\underbrace{rr\:x\:rr}$
$rr, rr, rr, rr$
$\underbrace{rr,rr,rr,rr}_{100\%}$

Therefore:
Crossing results in 100% (homozygous recessive).