# Unordered Tetrads

Online Science Education :: Subjects :: Biology :: Genetics :: 1 on 1 Tutoring

## Unordered Tetrads

AlwaysLearning wrote:I'm struggling on this too, please help. My deadline is tomorrow.

In a chlamydomonas cross AB X ab the following unordered asci were recovered (10points)

AB Ab aB ab 44

AB ab AB ab 85

Ab aB Ab aB 23

a. Label each class of Tetrads (P,NP.TT)

b. Determine the distance between the two genes

Thank you so much.

First, you need to understand what P, NP and TT stand for. P – parental ditype – is the same as parents. In this case parents are AB and ab, therefore, second tetrad AB ab AB ab is parental ditype. NP – nonparental ditype - contains 2 types of recombinant loci such as the third line: Ab aB Ab aB (two of each Ab type and aB type). Finally, TT – tetratype – is a tetrad with 4 different genotypes like the 1st line AB Ab aB ab (all different!)

Now that you know that you will be able to calculate the distance from the formula:

RF= (1/2 TT + NP)/(TT+NP+P) and the distance is RF x 100

Good luck!

**Alla**- Instructor
- Posts : 103

Join date : 2008-02-27

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