Chapter 4, Problem 17PDQ

In pigs, coat color may be sandy, red, or white. A geneticist spent several years mating true-breeding pigs of all different color combinations, even obtaining true-breeding lines from different parts of the country. For crosses 1 and 4 in the following table, she encountered a major problem: her computer crashed and she lost the F₂ data. She nevertheless persevered and, using the limited data shown here, was able to predict the mode of inheritance and the number of genes involved, as well as to assign genotypes to each coat color. Attempt to duplicate her analysis, based on the available data generated from the crosses shown.

Cross	P1	F1	F2
1	sandy $\times$ sandy	All red	Data lost
2	red $\times$ sandy	All red	3/4 red: 1/4 sandy
3	sandy $\times$ white	All sandy	3/4 sandy: 1/4 white
4	white $\times$ red	All red	Data lost

When you have formulated a hypothesis to explain the mode of inheritance and assigned genotypes to the respective coat colors, predict the outcomes of the F₂ generations where the data were lost.