Question

In maize, pure-breeding lines are obtained that have red, pink or orange kernels when exposed to sunlight. Normal kernels remain yellow in sunlight. The table below gives the results of three crosses between the lines.

Cross	Parent phenotype	F1 Phenotypes	F2 Phenotypes
1	red x pink	ALL RED	66 red, 20 pink
2	orange x red	ALL RED	988 red, 314 orange
3	orange x pink	ALL ORANGE	1300 orange,429 pink

A. How many genes are involved in color determination? Explain

B. What are the relationships between alleles and/or genes involved in the determination of red, pink, and orange phenotypes? You may ignore yellow in your answer. Be certain to define symbols and to state whether the relationships are dominant, recessive, codominant, etc. Explain your answers!!!

Answer 1

There are two genes which are involved in the determination of kernel colour. As there are three phenotypes that are present in the population. in case of dominant receive relation of one gene, only two phenotypes are possible. It is not a case of incomplete dominance as there are only phenotypes upon self crossing all the F1 progenies. So there are two genes that are involved in the cross.

The allele for red colour is dominant over pink as all the F1 progeny of cross 1 and 2 are red and also in F2 progeny the ratio of red to other colour is 3:1 Orange colour is dominant over pink as all the F1 progeny of cross 3 are orange and also in F2 progeny the ratio of orange to pink colour is 3:1.

Let the allele be R for red, o for orange and p for pink

Cross 1 RR crossed with pp - F1 progeny Rp self-cross - progenies = in 3:1 ratio

Cross 1 RR crossed with oo - F1 progeny Ro - self-cross - progenies = in 3:1 ratio

Cross 1 oo crossed with pp - F1 progeny op self-cross - progenies = in 3:1 ratio

Please write me back if you need more help.