Question

The Kidd blood group in primates is inherited as a single gene with two codominant alleles (Jka and Jkb). We would like to verify that this locus actually follows simple Mendelian inheritance with codominant alleles in gibbons. We have a pure breeding population of Type Jka and a pure breeding population of Type Jkb. We create an F2 population and test for the antigens.

Jka: 34

Jka Jkb: 81

Jkb: 34

Perform a chi square analysis on this data using the following hypothesis:

The mode of inheritance for the Kidd blood group in gibbons is simple Mendelian with codominant alleles.

Calculate the chi square value and place it in the space below. Round to three decimal places.

(How to calculate expected ratio? should it be 34/149 x 16, 81/149 x 16?)

Answer 1

Jka Jka x Jkb Jkb --------Paretns

       Jka Jkb --------------F1

F1 x F1

	Jka	Jkb
Jka	Jka Jka	Jka Jkb
Jkb	Jka Jkb	Jkb Jkb

Expected F2 ratio: Jka(1) : Jka Jkb (2) : Jkb(1) = 37.25 : 74.5: 37.25

Observed ratio = 34 : 81 : 34

Phenotype	Observed(O)	Expected (E)	O-E	(O-E)2	(O-E)2/E
Jka	34	37.25	-3.25	10.563	0.284
Jka Jkb	81	74.5	6.5	42.250	0.567
Jkb	34	37.25	-3.25	10.563	0.284
	149	149			1.134

Chi-square value = 1.134