Page 104 - Probability Demystified

CHAPTER 5 Odds and Expectation 93

What happens with two hybrid yellow plants?

Y g
YYYYg
g gY gg

1 1 1
Hence, PðYYÞ¼ , PðYgÞ¼ PðgYÞ¼ , and PðggÞ¼ :
4 2 4
What about a pure yellow plant and a hybrid yellow plant?

Y g
YYY Yg
YYYYg

1 1
Hence, PðYYÞ¼ and PðYgÞ¼ :
2 2
What about a hybrid yellow plant and a pure green plant?

g g
Y Yg Yg
g gg gg

1 1
Hence PðYgÞ¼ and PðggÞ¼ :
2 2
This format can be used for other traits such as gender, eye color, etc.
For example, for the gender of children, the female egg contains two X
chromosomes, and the male contains X and Y chromosomes. Hence the
results of fertilization are

X Y
XXX XY
XXXXY

1 1
Hence, PðfemaleÞ¼ PðXXÞ¼ and PðmaleÞ¼ PðXYÞ¼ :
2 2
Mendel performed experiments and compared the results with the
theoretical probability of the outcomes in order to verify his hypotheses.