In a sample of double stranded dna if 19% of the nitrogenous bases are guanine what percent of the nitrogenous bases are adenine

31%

Explanation:

Chargaff's law says the amount of A (adenine) = T (thymine) and G (guanine) = C (cytosine). If

G = 19% then C= 19%

19% + 19% = 38%

100% - 38% = 62%

62% for A and T

Divide by 2 and you get

31%

dna is made up of six smaller molecules -- a five carbon sugar called deoxyribose, a phosphate molecule and four different nitrogenous bases (adenine, thymine, cytosine and guanine).