You go online to see if these mutations are known, and you find that a drosophil

Question

You go online to see if these mutations are known, and you find that a drosophila lab at Purdue University has published that they have isolated flies with similar phenotypes. They give estimated linkage values of their trait loci to a third loci [sepia]. You want to prove [or not] that the Purdue linkage and distance is also accurate for your mutations – suggesting your mutant genes are the same as theirs. Explain your crosses and the expected results that would verify the genes are the same and the linkage relationship is true for your genes.

Explanation / Answer

Forward genetics = Phenotype to genotype.

The first step in a forward genetic screen is to isolate a new mutation which shows the desired phenotype. Once a mutant is isolated, the next step is to make sure that the mutation is novel and is not reported earlier for the given phenotype. For this purpose, a careful and detailed literature analysis must be done to check whether there are any reported mutants with the similar phenotype. If such mutants exist, we need check whether the isolated mutation is allelic to already established mutant.

For this, we need to obtain that reported mutant and cross it with the isolated mutant in the screen.

If the newly isolated mutant is allelic to the reported mutant, all the F1 progeny would show mutant phenotype.

If the newly isolated mutant is not allelic to the reported mutant, the F1 progeny would show WT phenotype and both the mutations will segregate in the F2 progeny.

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