In guinea pigs black coats are dominant to brown coats. A heterozygous rough, bl
ID: 72768 • Letter: I
Question
In guinea pigs black coats are dominant to brown coats. A heterozygous rough, black coated guinea pig is crossed with a homozygous recessive smooth, brown coated guinea pig
What are the possible gametes that the rough black guinea pig could make?
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What are the possible gametes that the smooth brown guinea pig could make?
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What are the genotypes of the offspring of this cross and what are the ratios that they would represent?
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What are the phenotypes of the offspring of this cross and what are the ratios that they would represent?
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If you used a Punnett Sqaure, what did it look like/how did you use it?
Explanation / Answer
Let the dominant allele for rough be ‘R’ and recessive allele be’r’
Likewise, let the dominant allele for black be ‘B’ and recessive be ‘b’
Gametes produced = RB, Rb, rB, rb
Gametes produced = rb, rb, rb, rb.
To find the genotypes of the cross between RrBb and rrbb, make a punnet square
rb
rb
rb
rb
RB
RBrb
RBrb
RBrb
RBrb
Rb
Rbrb
Rbrb
Rbrb
Rbrb
rB
rBrb
rBrb
rBrb
rBrb
rb
rbrb
rbrb
rbrb
rbrb
Genotypes:
Ratio = 1 : 1 : 1 : 1
Phenotypes:
Ratio = 1 : 1 : 1 : 1
rb
rb
rb
rb
RB
RBrb
RBrb
RBrb
RBrb
Rb
Rbrb
Rbrb
Rbrb
Rbrb
rB
rBrb
rBrb
rBrb
rBrb
rb
rbrb
rbrb
rbrb
rbrb