Chapter 2, Problem 4EQ

For all seven characters described in the data of Figure 2.5, Mendel allowed the ${\text{F}}_{\text{2}}$ plants to self-fertilize. He found that when ${\text{F}}_{\text{2}}$ plants with recessive traits were crossed to each other, they always bred true. However, when ${\text{F}}_{\text{2}}$ plants with dominant traits were crossed, some bred true but others did not. A summary of Mendel’s results is shown to the right.

${\text{F}}_{\text{2}}\text{ parents}$	True-Breeding	Non-True-Breading	Ratio
Round	193	372	1:1.9
Yellow	166	353	1:2.1
Gray	36	64	1:1.8
Smooth	29	71	1:2.4
Green	40	60	1:1.5
Axial	33	67	1:2.0
Tall	28	72	1:2.6
Total:	525	1059	1:2.0

When considering the data in this table, Page 45 keep in mind that they describe the characteristics of the ${\text{F}}_{\text{2}}$ generation parents that had displayed a dominant phenotype. These data were deduced by analyzing the outcome of the ${\text{F}}_{\text{3}}$ generation. Based on Mendel’s laws, explain why the ratios were approximately 1:2.