In Figure 217 how does the 31 ratio in the bottom lefthand g

In Figure 2-17, how does the 3:1 ratio in the bottom left-hand grid differ from the 3:1 ratios obtained by Mendel?

There is no difference between the 3:1 ratio in the figure and those that Mendel observed. The 3:1 ratio in the figure is the result of differences in a sex-linked gene. Mendel reported on only autosomal traits. The 3:1 ratio in the figure is occurring in an animal undergoing sexual reproduction, while Mendel observed his 3:1 ratios in plants. The 3:1 ratio in the figure is the result of a testcross. Mendel only observed 3:1 ratios in crosses between heterozygous individuals.

First cross XX X Y Red femal White male Male gametes Female gametes 1 Red 1 Red 2 female 2 male Male gametes 1 Red 1 Red Female 4 female 4 male gametes 1 White 1 Red 4 females 4 male Figure 2-17 Introduction to Genetic Analysis, EleventhEdition 02015 W.H. Freeman and Company Second cross XX X Y White female Red male Male gametes Female gametes 1 Red 1 White 2 female 2 male Male gametes Red 4 male 1 Red 4 female Female gametes w 1 White White 4 male 4 female

Solution

b)The 3:1 ratio in the figure is the result of differences in a sex-linked gene. Mendel reported on only autosomal traits.

The main aspect of 3 : 1 ratio is that all females usually have red eyes (X+/–).On the other hand half of the the males have red (X+/Y) and the other half have white (Xw/Y). This means that an in depth and a careful sex determination at the time of counting F2 offspring will usually lead to a sex linked trait which is given in the option b.