An experiment to determine the inheritance of flower color is snap dragons cross
ID: 81773 • Letter: A
Question
An experiment to determine the inheritance of flower color is snap dragons crossed two plants with pink flower. The following progeny were recorded from the cross. 92 plants had red flowers, 210 had pink flower and 98 had white flowers. a. Product how flower color is inherited in snap-dragons. i. red: ii. pink: iii. White c. Calculate the expected value for each phenotype given the inheritance pattern you predicted: d. Calculate the Chi-square value for the data. chi^2 = Sigma (observed-expected)^2/expected e. use the chi square table to interpret your data. Be sure to relate your findings to your original prediction of inheritance pattern.Explanation / Answer
A. From the no of flowers expressed, the ratio is approximately equal to 1 red: 2 pink : 1 white flower. It is an example of incomplete dominance. Here pink is more and hence it is predicted that it is heterozygous in nature and also exhibit incomplete dominant character. Whereas red and white are wild type homozygous varieties.
B. Based on (a) the genotype can be predicted as
Red : R/R
Pink : R/r
White : r/r
Lets check the cross
Parent pink R/r x R/r
Gametes R r x R r
F1 genotype R/R R/r R/r r/r
F1 phenotype 1 red, 2 pink, 1 white
Hence predictions are right.
C. Expected
Total no of flowers = 400
Red = 1/4*400 = 100
Pink = 1/2*400 = 200
White = 1/4*400 = 100
D. Chi square = (92-100)2 / 100 + (210 - 200)2 / 200 + (98 - 100)2 / 100 = 1.18
E. The degree of freedom = no of class - 1 = 3 - 1 = 2
For this degree of freedom and chi square value, the probability is Determined to be less than 0.5 or 50% (using chi square and probability table). The expected value is deviated by 50%. But from our problem, it is observed that there is only 5% deviation. Hence our predictions may be correct.
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