Complex sentence: Erwin Chargaff's work in 1950 demonstrated that in DNA the bases guanine and cytosine were found in equal abundance, and the bases adenine and thymine were found in equal abundance, although there was no equality between the amount of one pair versus the other.
Split into simpler sentences: Erwin Chargaff's work in 1950 demonstrated that, in DNA, the bases guanine and cytosine were found in equal abundance, and the bases adenine and thymine were found in equal abundance. However, there was no equality between the amount of one pair versus the other.