Question

(b) Morgan actually obtained the following results: 965 offspring were gray body/long wings; 944 were black body/vestigial wings, 206 were gray/vestigial and 185 were black/long. With this information fill in the goodness of fit table (table 5) and cal- culate x (c) The critical value for this test is still 7.815. Does Morgan's study support or contradict the claim that body color and wing length obey Mendel's Principle of Independent Assortment? Defend your answer.

Answer 1

Answer:

b).

The expected ratio of the above progeny would be 1:1:1:1.

Phenotype	Observed(O)	Expected (E)	O-E	(O-E)2	(O-E)2/E
Gray body / long wings	965	575.00	390.00	152100.00	264.52
black body / vestigial wings	944	575.00	369.00	136161.00	236.80
gray body/vestigial wings	206	575.00	-369.00	136161.00	236.80
black body / long wings	185	575.00	-390.00	152100.00	264.52
Total	2300	2300.00			1002.65

X^2 value = 1002. 65

Degrees of freedom = Number of phenotypes – 1

Df = 4-1=3

Critical value = 7.815

The chi-square value of 1002.65 is greater than the critical value of 7.815. We can reject null hypothesis and the two genes are linked.

c). Based on the above results, it is clear that if the two genes are present on the same chromosome, thery are said to be linked. Testcross ration of linked genes and genes assorted independently assorting genes are different.