Question

In Drosophila, the allele dp determines long wings and dp determines short ("dumpy") wings. At a separate locus e* determines gray body and e determines ebony body. Both loci are autosomal. The original parents were purebred with antagonistic traits, one of the parents had long wings and ebony body. The dihybrid F1 was test crossed with the following result: Long, ebony 151 Long, gray 136 Short, gray 140 Short, ebony 145 Total You want to determine if the data support whether the genes are linked or sort independently by using the chi squared test 572 a. State the null hypothesis for this experiment b. Calculate the chi squared value. c. Determine the degrees of freedom and give the p value range d. What is your conclusion? e. What was the genotype of the original parents? f. Show the linkage arrangement of the parents, the F1, the F1 tester, and the progeny

Answer 1

A- Out null hypothesis is that the gene assorts independently.

B-  

	Observed	Expected	O-E	(O-E)2	(O-E)2/E
Long ebony	151	145.5	5.5	30.25	0.207904
long gray	136	145.5	-9.5	90.25	0.620275
short gray	140	145.5	-5.5	30.25	0.207904
Short ebony	145	145.5	-0.5	0.25	0.001718
Total	572			0	1.037801

C - The degree of freedom is given by the number of phenotypes1-

So the degree of freedom df = 4-1 = 3

D- For the degree of freedom 3 when the p-value is 0.05 chi-square value is 7.8. So our hypothesis is valid and genes are assorted independently.

E- Genotype of parent dp+dp+ ebeb and dpdp eb+eb+

F-

Parent dp+ eb dpt eb dp eb+ dp ebt F1 dp+ eb+ dp eb F2 progeny dp* ebtdp* ebdpebt