Chemistry · Ch 10 — Biomolecules
Biological Functions of Nucleic Acids
Biological Functions of Nucleic Acids
DNA: the chemical basis of heredity
DNA is the chemical basis of heredity — it can be thought of as the cell's permanent reserve of genetic information. It is DNA that is exclusively responsible for maintaining the identity of a species, essentially unchanged, across countless generations spanning millions of years.
This is possible because a DNA molecule is capable of self-duplication during cell division: when a cell divides, its DNA makes an identical copy of itself, and one complete copy is transferred to each of the two daughter cells. This copying process (replication) is what allows hereditary information to be passed on faithfully from a cell — and, ultimately, from a parent organism — to its offspring.
The complementary base-pairing described in §10.5.2 (A pairs only with T, G pairs only with C) is precisely what makes faithful self-duplication possible: since each strand of the double helix already specifies the exact sequence of its partner strand, either strand can serve as a template from which an identical complementary copy can be reconstructed. This is the chemical reason "identical copies of parental DNA pass on to daughter cells."
DNA, RNA, and protein synthesis
The other major biological function of nucleic acids is directing protein synthesis in the cell. Here the two nucleic acids play distinct, complementary roles:
- The message — the instructions for building a particular protein — is stored in DNA.
- The actual synthesis of the protein, however, is carried out by various RNA molecules in the cell, not by DNA directly. …