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Plz help  question on probabilty of a nucleotide sequenceModerator: BioTeam
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Plz help  question on probabilty of a nucleotide sequenceFirst off the Question: Please let me know if I am on the right path or missing something?
A molecule of doublestranded DNA that is 5 million base pairs long has a base composition that is 62% G + C. How many times, on average, are the following restriction sites likely to be present in this DNA molecule? (a) BamHl (recognition sequence = GGATCC) My attempt at solving it: (.19) chance of getting an A or T (.31) chance of getting a C or G To get AAGCTT I first calculated the probability of that sequence occuring in a row: (.31)(.31)(.19)(.19)(.31)(.31) = 0.0003339 I then multiplied this probabilty by the number of total nucleotides that occuring in 5 million base pairs which is 10 million. Therefore (0.0003339)(10,000,000) = 3333.4 would be my answer However, I was thinking about dividing this answer by 6 because the sequence cannot possibly occur more than once every 6 nucleotides. IE. The sequence AAGCTTAAGCTT is 12 nucelotides long but the sequence could never occur more than twice. So my final answer to the original question above would be 3333.4/6 which gives 555.7 restriction sites would be likely to be present in this DNA molecule of 5,000,000 base pairs.
Re: Plz help  question on probabilty of a nucleotide sequence
But I think with this formula, the order doesn't matter, rigth? http://www.biolib.cz/en/main/
Cis or trans? That's what matters.
Re: Plz help  question on probabilty of a nucleotide sequence
So, permutation of a sequence which has 6 elements with two repetitions (As and Ts): 6!/(2!).(2!)=180 Which means there are 180 permutations of 6 bp sequence that is consisted of 2 As, 2 Ts, 1 G and 1 C. So, you should divide your answer by 180: 555.7/180=3.1 I think rest of the calculations seems correct. But, I didn't understand why you did the calculation for AAGCTT sequence while your sequence is GGATCC?
Re: Plz help  question on probabilty of a nucleotide sequencebut the formula
is for sequence of 2 A/T and 4 C/G http://www.biolib.cz/en/main/
Cis or trans? That's what matters.
Re: Plz help  question on probabilty of a nucleotide sequenceYes, I see it now that the calculation is for the sequence given by the question. So, the answer should be 3.
This sentence made me ask it. I guess james0222 mistyped it.
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