1920 JA Moore investigated the inheritance of spotting patte

19-20.  J.A. Moore investigated the inheritance of spotting patterns in leopard frogs (J.A. Moore, 1943, Journal of Heredity 34:3-7).  The pipiens phenotype had the normal spots the give leopard frogs their name. In contrast, the burnsi phenotype lacked spots on its back. Moore carried out the following crosses, producing the progeny indicated.

cross#            Parental phenotypes               Progeny phenotypes

1                    burnsi x burnsi             39 burnsi, 6 pipiens

2    burnsi x pipiens   23 burnsi, 29 pipiens

3    burnsi x pipiens                    196 burnsi, 210 pipiens

19.  On the basis of these results, what is the most likely mode of inheritance of the burnsi phenotype (i.e., dominant or recessive). Assign alleles associated with each trait. Give the genotype of the parents in each cross.

20.  For cross number 3 (in the table), use a chi-square test to evaluate the fit of the observed number of progeny to the number expected on the basis of your proposed genotypes (and proposed mode of inheritance).

please answer both of these with explanation, very confused how to do this. Thank You

Solution

19. The results of burnsi x brunsi suggeset that the individuals are heterozygous with both brunsi (B) and pipiens (B⁺)alleles.

brunsi (BB⁺) x brunsi (BB⁺)

brunsi (BB⁺) x pipiens (B⁺B⁺)

brunsi (BB⁺) x pipiens (B⁺B⁺)

The cross also predicts that brunsi is dominant and pipiens is recessive. The two crosses of brunsi x pipiens suggest that they are between homozygous recessive (pipiens) and heterozygous dominant (brunsi) individuals.

20. For the cross of brunsi (BB⁺) x pipiens (B⁺B⁺) we would expect a phenotypic ratio of 1:1 in offsprings

As there are two phenotypic classes the degree of freedom is one(1). From the chi square table the values fall between 0.45 (P 0.5) and 2.706 (P .1). The probability of difference between what we observed and what was expected is generarted by chance and the parents are as predicted (BB⁺ and B⁺B⁺).