1: DNA, Genes, Chromosomes and Genome
The molecular foundation of all living organisms lies in DNA — deoxyribonucleic acid — a remarkable molecule that encodes the instructions needed for growth, development, and reproduction. DNA is organized into genes , the functional units of heredity, which guide the production of proteins that determine the structure and function of cells. These genes are meticulously arranged on chromosomes , thread-like structures within the cell nucleus that ensure accurate distribution of genetic information during cell division.
Collectively, an organism's complete set of DNA, including all its genes, is known as its genome . The human genome, for instance, spans over 3 billion base pairs and contains about 20,000-25,000 genes distributed across 23 pairs of chromosomes. Understanding the interplay between DNA, genes, chromosomes, and the genome is crucial for exploring the complexity of genetic inheritance, disease mechanisms, and the diversity of life. This chapter delves into the intricate architecture and function of these genetic elements, providing a foundation for the study of molecular biology and genetics.