restriction enzyme question

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Newbie90

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For the following restriction endonucleases, calculate the average distance between
restriction sites in an organism whose DNA has a random sequence and equal
proportions of all four nucleotides (25% each of A, T, C and G). The symbol R means
any purine (A or G), Y means any pyrimidine (T or C), and N stands for any nucleotide
(A, T, C or G).

Sau I
5' CCTNAGG 3'

RsaI
5' GTAC 3'

CviII
5'-RGCY-3'

I know how to do the RsaI and I got 1 out of 256 ie; 1/(4^4)

how do I do Sau I when there is the letter N or Y/R?

would the probability be 1 or 100% for N? and 50% for y/r?

thanks.

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Not sure if I got this right:

since they are equal, you have 7 nucleotides in Sau I:
0.25^7 = 6.1 x 10^-5 which is about 16393 bp
 
Not sure if I got this right:

since they are equal, you have 7 nucleotides in Sau I:
0.25^7 = 6.1 x 10^-5 which is about 16393 bp


Ok. What about cvil?

would you say that for each R or Y the probability would be 0.5?
 
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CviII
5'-RGCY-3'

There is a faster way to do it too:

4^2 x 2^2 = 16 x 4 = 64 bp
 
don't fill ur brain with useless bio questions :) practice with material that is the same difficulty for bio b/c u don't want to learn the stuff that doesn't matter, concepts and understanding are tested in bio, they won't ask u for these silly questions. they don't want to know whether u can add or not, that part is for quant.
 
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