Question

In: Biology

You mate a male from a true-breeding strain of dwarf mice to a female from a...

You mate a male from a true-breeding strain of dwarf mice to a female from a true-breeding normal-sized strain. The F1 mice are all normal in size. What would the phenotypes of the F1 and F2 mice be in the reciprocal of the above cross if the dwarf character is caused by a mitochondrial genome defect?

Solutions

Expert Solution

In maternal effect also referred to as maternal influence, phenotype of the progeny for particular trait is under the control of mitochondrial DNA contributed by the egg. Unlike nuclear DNA which is contributed by both the parents to the offspring, mitochondrial DNA is only contributed by the mother.

(Male) DD = for the normal in size

(Female) dd = for the dwarf character

From the question we observed that the dwarf character is caused by a mitochondrial genome defect, and we know that mitochondrial DNA is contributed by the mother only.

In maternal inheritance, Progeny phenotype is depends on the genotypes of female parents.

Parental cross DD (Male)   X   dd (Female)   

M & F

(Female) d

  (Female)    d

(Male) D

Dd

Dd

(Male)   D

Dd

Dd

NOTE : F1 generation will be 100% dwarf phenotypically because mitochondrial DNA is contributed by the mother and mitochondrial DNA has the dwarf character defect.

  • The dwarf pattern of progeny mice is determined by the genotype of the parent producing the egg, regardless of the phenotype of that parent.

F 2 generation

In maternal inheritance, If the female genotype does control the phenotype of its offspring regardless of female phenotype, then we would predict that all the F2 generation mice would have normal height.


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