Yellow coat color in guinea pigs is produced by the homozygous genotype, YY, and white is...

Yellow coat color in guinea pigs is produced by the homozygous genotype, YY, and white is produced by the homozygous genotype, yy. One homozygous yellow guinea pig crosses with a homozygous white guinea pig to produce cream guinea pigs. a. What pattern of inheritance does this follow (complete, incomplete or co-dominance)? How do you know? b. Draw a Punnett square for a cross between two cream guinea pigs. What are the genotypic and phenotypic ratios?

Expert Solution

Answer:

a. This example follows the inheritance pattern of incomplete dominance.

In this cross between a pure breed with dominant genotype YY which shows yellow coat colour and a pure breed with recessive genotype yy which shows white coat colour, the progeny shows cream coloured coats. This shows that there is blending of characters thereby proving that it is an incomplete dominance.
In incomplete dominance both the factors are unable to express their characters completely resulting in an intermediate type of generation.

b. The cream coloured guinea pigs have genotype Yy. A cross between two such guinea pigs is as shown below:

The genotypic ratio is 1 : 2 : 1 (YY : Yy : yy) - this ratio is same as genotypic ratio of Mendelian monohybrid cross.
The phenotypic ratio is 1 : 2 : 1 (Yellow : Cream : White) - this ratio is different from a typical monohybrid cross which has phenotypic ratio as 3 : 1

gladiator answered 2 years ago

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