Question

Wheat kernels can be red, brown, or white. When true breeding reds are crossed with true breeding whites, all the offspring are brown. When these F1s are crossed you get the following results: 1883 Red kernels 1232 Brown kernels 197 White kernels There are varieties of brown, however, that are also true breeding. State a genetic hypothesis for inheritance of kernel color and test the above data for your hypothesis.

Answer 1

The observed values i.e. 1883 : 1232: 197 almost fit to 9:6:1 ratio, which indiates that the kernal colour is driven by Duplicate genes with cumulative effect interaction.  In this type of gene interaction the dominanat allele at boht loci determines the full trait color, where as the recesseive alleles at both loci determines color phenotypes and dominant loct at either of loci will exhibit intermiediate phenotype.

Null hypothesis: The observed values are not deviating from the expected Duplicate genes with cumulative effect ratio i.e. 9:6:1.

Test static:

Categories	Red	Brown	White	Total
Observed values (O)	1883.00	1232.00	197.00	3312
Exptected Ratio (ER)	9	6	1	16
Exprected Values (E)	1863	1242	207
Deviation (O-E)	20	-10	-10
D^2	400	100	100
D^2/E	0.214707	0.080515	0.483092	0.778315
X^2	0.778315
Degrees of freedom	3-1=2

Inference: The calculated chisquare value i.e. 0.77 is less than the table value i.e. 5.99 at 0.05 probability and 2 DF, hence the null hypothesis is accepted which means that Duplicate genes with cumulative effect the kernel color.