restrict. frag. freq. distrib.
Zharkikh Andrey
gsbs1022 at utsph.sph.uth.tmc.edu
Fri Jan 15 14:31:47 EST 1993
eric at tomcat.onr.navy.mil ((Eric Eisenstadt)) writes:
>Is there a general and straightforward way to calculate the frequency
>distribution of different length restriction fragments generated by cutting
>a genome of size N with a specified set of restriction fragments? For
>example, how many different 3 kb fragments are expected to result from
>digesting a 4 x 10E6 bp genome with two different six-cutters?
Let p is the frequency of six-cut sites.
[p=4^(-6)=1/4096 for equal base content].
Then the expected # of fragments of all sizes is M=N*p,
where L is the genome size.
[N=4,000,000; M=977].
The probability of a fragment of size k > K is Prob(k>K)=(1-p)^k.
for K=3000, Prob(k>3000)=(1-1/4096)^3000=0.48
The expected number of such fragments is m=M*Prob(k>K)
m=977*0.48=469
For an interval of sizes: Prob(K1<k<K2)=Prob(k>K1)-Prob(k>K2).
say, for K1=3000 and K2=3100, Prob=0.48-0.47=0.01;
m=977*0.01=9.7
That's what you asked?
Andrey.
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