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GENETICS: Please explain the following. 1 Assume baldness is determined by one g

ID: 133567 • Letter: G

Question

GENETICS: Please explain the following.

1 Assume baldness is determined by one gene and is recessive. If two heterozygous parents have six childrer What is the probability that all 6 will be normal- What is the probability that all 6 will be bald- What is the probability that at least one is normal What is the probability that at least one is bald- 2 An X-linked dominant allele causes hypophosphatemia in humans. A man with hypophosphatemia marries a normal woman. What proportion of their sons will have the disease? What proportion of their daughters will have the disease?

Explanation / Answer

Answer:

1).

B_ = Normal

bb = Bald

Bb x Bb ----Parents

B

b

B

BB (normal)

Bb (normal)

b

Bb (normal)

bb (bald)

Normal = ¾

Bald = ¼

The probability that all 6 will be normal = ¾ * ¾ * ¾ * ¾ * ¾ * ¾ = 729 / 4096 = 18%

The probability that all 6 will be bald = ¼ * ¼ * ¼ * ¼ * ¼ * ¼ = 1 / 4096 = 0.02%

The probability that atleast one is normal = ¾ * ¾ * ¾ * ¾ * ¾ * ¼ = 243 / 4096 = 5.93%

The probability that atleast one is bald = ¼ * ¼ * ¼ * ¼ * ¼ * ¾   = 3 / 4096 = 0.07%

2).

Man( XH Y) x Woman (Xh Xh)---Parents

Xh

XH

XH Xh (daughter with disease)

Y

Xh Y (normal son)

No son will have the disease.

100% of their daughters will have the disease.

B

b

B

BB (normal)

Bb (normal)

b

Bb (normal)

bb (bald)