Breeding show chickens, you identify a novel feather pattern gene, Pg. Segregati
ID: 215853 • Letter: B
Question
Breeding show chickens, you identify a novel feather pattern gene, Pg. Segregation ratios between it and another feather color gene, Melanotic (Ml) seem a little off and you believe there might be genetic linkage between these 2 loci. To test this hypothesis, you perform some mapping crosses as follows:
P: Pg/Pg ; ml/ml X pg/pg ; Ml/Ml
(patterned, pale pigment) (unpatterned, dark pigment)
F1: Pg/pg ; Ml/ml X pg/pg ; ml/ml
(patterned, dark pigment) (unpatterned, pale pigment)
Progeny:
Phenotype
Number observed
patterned, pale pigment
29
unpatterned, dark pigment
30
patterned, dark pigment
22
unpatterned, pale pigment
19
Does this data support the hypothesis of genetic linkage? Run a Chi-square test. Show how you determined this.
Phenotype
Number observed
patterned, pale pigment
29
unpatterned, dark pigment
30
patterned, dark pigment
22
unpatterned, pale pigment
19
Explanation / Answer
null hypothesis = genes are independently assorted and show no linkage.
This is a test cross (F1 crossed wih homozygous recessive)
so the ratio should be 1:1:1:1
total individuals is 100 so expected number of offsprings for each genotype will be 25
Chi square= (Observed- expected)2/expected
(29-25)2/25+ (30-25)2/25+ (22-25)2/25+ (19-25)2/25
16+25+9+36/25= 3.44
degree of freedom= 3
P value at 0.05 for df =3 is 7.84
P value is greater than 3.44 so we accept the null hypothesis and reject the alternate hypothesis that genes show linkage.