8. (11 points) Albinism is a skin pigmentation disease and is controlled by a si

Question

8. (11 points) Albinism is a skin pigmentation disease and is controlled by a single gene. Albinism is a recessive trait and the mutant form is "a". Consider a marriage between two normal individuals, both of whom are known carriers (Aa). h. If they have four children, what is the probability that two will be albino? i. What is the probability that the father will produce an a" gamete? j. What it the probability that the first child will be an albino girl? k. In a study on a large number of families in which both parents are known to be carriers, a total of 128 normal and 22 albino children were observed. Do the numbers deviate significantly from expected? Calculate the Chi square value, degrees of freedom, and

Explanation / Answer

If a marriage between two normal carriers happen, then their kids will be

Aa X Aa

AA Aa Aa aa

h) the probability of one child being albino (aa genotype) is 1/4

therefore the probability of 2 children being albio are 1/4 * 1/4 = 1/16

i) The father can produce two types of gametes A and a.

therefore the probability is 0.5

j) we alredy know the probability of an alibino is 1/4

the probability of a child being girl is 1/2

therefore the probability of a child being girl and albino is 1/4 * 1/2 = 1/8

k) given that

Observed probability = 22/150 = 15% (approximately)

Expected probability = 25% (calculated previously)

Therefore there is a difference in the observed probabilities.

chi-square value = (observed - expected)2 / expected

= (15 - 25)2 / 25

= 4

degree of freedom = number of samples -1

= 2 - 1. = 1

# of Childen Normal 128 Albino 22 total 150

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