Suppose you identified two new mutations in Spartan fruit flies (Drosophila spar

Question

Suppose you identified two new mutations in Spartan fruit flies (Drosophila spartanensis). One mutation, 'Spartan body', results in the entire body being green with a white 'S' marking on the thorax, whereas the body color of wildtype flies is tan and without markings. A second mutation, 'hopper legs', shows very muscular legs, whereas the legs of wildtype flies are thin. Let's also say that you were able to culture true-breeding populations of both mutations and then you tested the inheritance of each by performing a set of reciprocal crosses with true breeding flies. Below are the F_1 and F_2 progeny of these crosses: A. By what mode (chromosome type & dominance) is the 'Spartan body' mutation inherited? B. By what mode (chromosome type & dominance) is the 'hopper leg' mutation inherited? C. Calculate the chi square test statistic (x^1 Stat) for the Reverse Cross that would be appropriate for testing whether you can safely reject the idea that these traits are independent (unlinked). Show your work. D. Determine the appropriate chi square critical value (chi^2_crit) for this test. E. What is the p range for a Type 1 error for these data? F. Are the two mutations linked? What specific piece(s) of offspring evidence led (leads) to that conclusion?

Explanation / Answer

A.) Spartan body:

Chromosome: Autosomal trait

Reason: Almost equal number of males and females were affected in the given observation. while in case of sex-linked traits more or less, female or male should show the character. Another reason is trait showed same pattern of inheritance in both forward and reciprocal cross.

Mutant trait: Dominant

reason: Dominant trait should not skip genegration. In the above observation spartant body type mutant trait observed in both F1 and F2 generation.

B.) Hopper leg

Chromosome: Autosomal trait

Reason: Almost equal number of males and females were affected in the given observation. While in case of sex-linked traits more or less, female or male should show the character. Another reason is trait showed same pattern of inheritance in both forward and reciprocal cross.

Mutant trait: Recessive

reason: Recessive trait skip genegration. In the above observation hopper leg type mutant trait was not observed in both F1, while express in F2 generation.

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