In a transformation experiment, DNA of a p+q+ strain was used to transform a rec

Question

In a transformation experiment, DNA of a p+q+ strain was used to transform a recipient strain that is auxotrophic for these markers. The number of each class of transformants is shown below:

Class    Genotype    Number

1 p+q+ 405

2 p+q- 300

3 p-q+ 195

a) If the total number of transformants isolated was 900, what is the co-transformation frequency for the p and q loci?

b) Diagram how each class of transformants were obtained starting with the recipient auxotroph. You should include one diagram of the recipient auxtroph, one diagram of the event that led to class 1, one diagram of the event that led to class 2, and one diagram of the event that led to class 3. Hint: For an example of a similar diagram see figure 5-11, page 177, in the textbook.

Explanation / Answer

a)

Based on the given data, the formula for calculation of co-transformation frequency of p and q loci are:

And the p+q+ strain co-transformation frequency is (405/900) ×100 = 0.45 or 45%

b)

For example, consider a new strain B- with genotype: p+q-. So, it needs metabolite “q” to grow. It can grow media does not contain “p” substance. A strain A- with genotype: p-q+. So, it needs metabolite “p” to grow. It can grow media does not contain “q” substance.

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