AP bio unit 6

what did Rosalind Franklin perform in the 1950’s? what did this reveal?

She performed x-ray crystallography of DNA, which revealed a pattern that was regular and repetitive

what did Edward Chargaff do during the time of Rosalind’s discoveries? What rules did he discover?

he analyzed DNA samples from different species. he found that the amount of adenine equals the amount of thymine, and that the amount of guanine equals the amount of cytosine.

describe the structures of purines and pyrimidines (nucleotides)

purines- double ring structure (A, G)

pyrimidines- single ring structure (C,U,T)

what are the base pairs of nucleotides held together by?

hydrogen bonds

how many hydrogen bonds do adenine and thymine have? What about cytosine and guanine?

adenine and thyme have 2, while cytosine and guanine have 3.