Final answer:
The number of adenine bases in a 100-base pair DNA double helix can be determined using the complementary base pairing rules. If there are 45 cytosine bases, there must be an equal number of adenine bases.
Step-by-step explanation:
DNA, or deoxyribonucleic acid, is a molecule containing the genetic instructions for the development and functioning of all living organisms. It consists of two intertwined strands forming a double helix, with sequences of nucleotides representing genetic information.
The number of adenine (A) bases in a 100-base pair DNA double helix can be determined by using the complementary base pairing rules. Adenine always pairs with thymine (T), and guanine always pairs with cytosine (C). So, if there are 45 cytosine (C) bases, there must be an equal number of guanine (G) bases. Therefore, the number of adenine (A) bases will also be 45, because A-T base pairs and G-C base pairs are always present in equal amounts in DNA.