What pattern did Erwin Chargaff discover in nitrogen bases?
1)The number of adenine bases is always equal to the number of thymine bases, and the number of cytosine bases is always equal to the number of guanine bases.
2)Complimentary base pairing of nitrogen bases in DNA is different for each life form on Earth.
3)In a DNA molecule, adenine always pairs with uracil and guanine always pairs with cytosine.
4)All life forms on Earth contain the same number of adenine, guanine, thymine, and cytosine bases.