Question

It has been proposed that the presence of black markings on the throat of kung fu geckos is coded by a dominant allele (B) and that the absence of such markings is coded by a recessive allele (b). To test this idea, heterozygous individuals are crossed (Bb x Bb) producing 500 offspring of which 350 have black markings and 150 don’t have black markings. Based on a punnett square, the expected phenotypic ratio for black markings to no black markings is 3:1.

Required:
Write down the correct statistical approach to test if the data is consistent with the expected 3:1 ratio.

Answer 1

See the answer below

Step-by-step explanation:

The correct statistical approach to test if the data is consistent with the expected 3:1 ratio would be the Chi square.

Chi-square =
`((O - E)^2)/(E)` where O = observed frequency and E = Expected frequency. In this case:

Phenotype O E Chi square

• Blacks 350 3/4 x 500 = 375
  `((350-375)^2)/(375)` = 1.67

• Non blacks 150 1/4 x 500 = 125
  `((150-125)^2)/(125)` = 5

Total Chi square = 1.67 + 5 = 6.67

Degree of freedom = 1

Tabulated Chi square = 3.841

Since the calculated Chi-square is more than the tabulated value, the null hypothesis is rejected and we conclude that the data is not consistent with the expected 3:1 ratio.