What technology advancement was necessary before scientists could begin to observe cells

In dna, only the_ varies from one nucleotide to another. base phosphate sugar amino acid

The seed coat's most important function is to provide a) a nonstressful environment for the megasporangium. b) the means for dispersal. c) dormancy. d) a nutrient supply for the embryo. e) desiccation resistance.

Dna has unique properties that allow it to accurately retain genetic information, even after multiple rounds of replication. one aspect of dna that allows it to accurately store genetic information is the base pairing from chargaff\'s first rule of the four nucleotide bases. if the c content of a dna molecule is 22%, what are the percentages of the remaining bases?