Calculate DNA base

[casper22]

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For some reason I cannot remember the formula to do these problem,...

Can someone please refresh my memory...

Here is the question...

If a DNA double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain






Ans: 75

 

[loveoforganic]

200 nucleotides total

AT
GC

25 A's means there are 25 T's.

200 - 50 = 150 left to account for, and those have to be made up of G and C (assuming typical watson cricke pairing).

 

[casper22]

Thanks dude...

Got it...So the formula is A+T = G+C = nucleotides...

 

[CompS]

Thanks dude...

Got it...So the formula is A+T = G+C = nucleotides...

I believe the correct formula is A + G = T + C. That's Chargraff's rule.

 

[mustardseed5]

#purines must = #pyrimidines