Chapter 17, Problem 1P

Reciprocal crosses of experimental animals or plants sometimes give different results in the ${\text{F}}_{\text{1}}$. What are two possible genetic explanations? How would you distinguish between these two possibilities (i.e., what crosses would you perform, and what would the results tell you)?

Summary Introduction

To analyze:

Reciprocal crosses of trial animals or plants, sometime give dissimilar results in ${\text{F}}_{\text{1}}$ generation. The two possible genetic explanations for the same has to be written. Also explain the approach that distinguishes between these two possibilities. i.e., the crosses performed, and the results obtained.

Introduction:

The reciprocal cross is a duo of crosses between a male of one strain and a female of other and vice versa. It is used to investigate the role of parental sex on a given inheritance pattern. It is used to identify whether the allele is present on an autosome or on the sex-chromosome.

Explanation of Solution

In the reciprocal cross, the parental genotype is reversed to test the role of the paternal sex on the inheritance pattern. If the F $\text{1}$ progeny of the reciprocal cross gives the same ration, it is considered that the alleles reside on the autosome while when the F $\text{1}$ result of the reciprocal cross differs from each other, it indicates that the allele resides other than autosome.

The other than autosome allele can either be inherited from the sex chromosome or by parental inheritance. In parental inheritance, two possible explanations for the change in result would be-

1. Homoplasmy - homoplastic cells have organelles with the same genotype.

2. Heteroplasmy - Heteroplasmic cells contain a mixture of the allele.

Conclusion

The reciprocal cross shows a different result in F $\text{1}$ generation because of the allele inherited from other than autosome.