How many guanines are found in a ds DNA that has 700 hydrogen bonds and 10% adenines?
Dear Student!
If the percentage of Adenine is 10% then the % of Thymine would also be 10% as they base pair by two hydrogen bonds with each other. Guanine makes 3 hydrogen bonds with cytosine and they make up 90% of the DNA.
Lets make some equations:
Assume number of A=T to be x and G≡C to be y, then according to the problem,
2x + 3y = 700; because A=T makes 2 hydrogen bonds and G≡C makes 3 hydrogen bonds
we can make another equation
y = 9x; because the DNA has 10% A=T and 90% G≡C
By solving these two equations the number of guanine residues come out to be approximately 217