Question

What is the probability that all four are normal? That three will be normal and one albino? Two normal and two albino? One normal and three albino? All four albino?

Answer 1

When both parents are heterozygous (Cc) carrier, in each pregnancy there is 25% chance of birth of an albino i.e. 1 in 4. So, in each pregnancy, there is 75% chance of birth of a normal (phenotypic) child i.e. 3 in 4.

Probability of birth of all normal :

3

4

X

3

4

X

3

4

X

3

4

approx 31%

Probability of birth of all albino :

1

4

X

1

4

X

1

4

X

1

4

approx 0.39%

Probability of birth of two normal and two albino:

3

4

X

3

4

X

1

2

X

1

2

approx 3.5%

Probability of birth of one normal and three albino:

3

4

X

1

4

X

1

4

X

1

4

approx 1.1%

Answer 2

Answer:

Albinism in humans is controlled by a recessive gene (c) . From marriages between (Cc). Assume that such marriage (Cc x Cc) 4 children are produced.