Question

if a dna double helix is 100 nucleotide pairs long and contains 25 adenine bases, how many guanine bases does it contain? 150 25 200 50 75 submit previous answers request answer incorrect; try again; 4 attempts remaining the sum of adenine and thymine bases equals 50.

Explanation:

Step1: Recall base - pairing rules

In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). So, the number of A equals the number of T, and the number of G equals the number of C.

Step2: Calculate the number of A - T pairs

Given there are 25 adenine (A) bases. Since A = T, there are also 25 thymine (T) bases. The total number of A - T pairs is 25 + 25=50 bases.

Step3: Calculate the number of G - C pairs

The DNA double - helix is 100 nucleotide pairs long, so it has 200 bases in total. Subtract the number of A - T bases from the total number of bases. The number of G - C bases is 200-(25 + 25)=150. Since G = C, the number of guanine bases is $\frac{150}{2}=75$.

Answer:

75