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Please consider the following question:

You cross Drosophilia and receive the following offspring: 965 wild-type, 944 black- vestigial, 206 gray- vestigial, and 185 black- normal. Explain your results and give the recombination frequency.

I would like to know how to determine what the parental type is here so I can then find the recombination frequency. I know that recombination frequency is equal to the total number of recombinants divided by the total number of offspring. In order to determine the total number of recombinants I must know the parental types. My teacher stated that the parental types are the ones that are most prevalent in number after a cross, but there are occasions in which this does not work.

Is there a more 'concrete' way to determine which are the parental types?

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Do you understand why parental type should be the most prevalent ? –  biogirl Apr 1 at 2:50
Your question is not very clear. Please add details or clarify. –  WYSIWYG Apr 1 at 7:30
The way that your teacher describes is a way used by most of the introductory biology student. If you understand why that way is correct, it will seem more "concrete" to you. It is because there is less probability of having recombinants. –  biogirl Apr 14 at 16:41

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