Introduction

The previous chapter covered inheritance patterns, but at Mendel's time nobody knew what the underlying 'factors' actually were. It took the better part of a century of research to establish that DNA — deoxyribonucleic acid — is the genetic material in most organisms. You already know from Class XI that nucleic acids are polymers of nucleotides, and that DNA and RNA are the two nucleic acids found in living systems. DNA carries genetic information in most organisms; RNA, while it does serve as the genetic material in some viruses, is mostly a messenger — though it also plays adapter, structural, and even catalytic roles. The complete sequencing of the human genome over the last decade opened up an entirely new field, genomics, which this chapter also touches on. But first, let's understand the structure of DNA itself, why it's the dominant genetic material, and how it relates to RNA.