In: Biology
In Triskelian cats, in the Blondish Galaxy, black coat color is dominant over grey. Coat color is determined by a single autosomal gene with two alleles:
B = black coat color; b = grey coat color.
The autosomal gene for eye color is hypothesized to assort independently from the gene for coat color. The two alleles are:
R = green eye color; r = blue eye color.
If a green-eyed black female cat whose mother has a grey coat and whose father has blue eyes mates with a blue-eyed grey male cat, use the Chi-Square goodness of fit test to determine whether the following counts of 1000 F1 offspring in Table 1 are consistent with the two-locus mode of inheritance, specifically independent assortment.
The threshold for a significance level of 5% for the Chi-square test with 3 degrees of freedom is 7.8150.
Table 1. Observed counts for two cat phenotypes.
Category | Coat Color | Eye Color | Observed Count |
1 | Grey | Green | 155 |
2 | Grey | Blue | 176 |
3 | Black | Green | 367 |
4 | Black | Blue | 302 |
NOTE: THIS IS A HARD QUESTION. YOU MUST DO SEVERAL CALCULATIONS.
A. REJECT, because the Chi-Square Value is 446.831.
B. REJECT, because the Chi-Square Value is 123.576.
C. REJECT, because the P-Value is 57.224.
D. ACCEPT, because the P-value is 1E-04 < 7.815.
E. REJECT, because the P-value is 1E-04 < 0.05.
Ans:
B. REJECT, because the Chi-Square Value is 123.576.
Explanation: If a green-eyed black female cat whose mother has a grey coat and whose father has blue eyes mates with a blue-eyed grey male cat, green-eyed black, green-eyed blue,blue-eyed black and blue-eyed grey offspring are produced in 1:1:1:1 ratio. The cross is given below-
The calculated chi-square value 123.576 is much higher than the table value 7.8150 at 3 DF (5% probability). The deviation between observed and expected value is not good fit. So, the assumed hypothesis 1:1:1:1 is rejected. This significant deviation is due to faliure of independent assortment.
All other options are incorrect because the calculated chi-square value is 123.576 and the assumed hypothesis is rejected.