Genetics, genes, DNA and RNA

Genetics is the study of heredity — how characteristics pass from parents to offspring — and of the molecules that carry biological information. At its centre is DNA, deoxyribonucleic acid, a long molecule shaped like a twisted ladder, or double helix, whose rungs are pairs of chemical bases. The order of these bases along the molecule spells out instructions, and a segment of DNA that codes for a particular product or trait is called a gene. In most organisms DNA is packaged into structures called chromosomes within the cell.

The information in DNA is put to use through RNA, ribonucleic acid, a related molecule that helps convert genetic instructions into proteins. In gene expression, a gene is first copied into a strand of RNA, which then guides the assembly of a protein from amino acids according to the genetic code. The genetic code is the set of rules by which sequences of three bases specify particular amino acids, a system shared across nearly all living things.

Genetics also explains patterns of inheritance. Building on the work of Gregor Mendel, scientists describe how versions of genes, called alleles, are passed on and how dominant and recessive forms produce observable traits. Comparing genes across species reveals shared ancestry, a homology that makes laboratory organisms such as the mouse valuable for studying human biology. Modern genetics extends to mapping where genes lie, studying stem cells, and techniques such as cloning, all built on the same foundation of DNA, RNA and the code they carry.

Frequently asked questions

What is a gene?

A gene is a segment of DNA that carries the instructions for a particular product or trait; genes are arranged along structures called chromosomes.

How do DNA and RNA differ in their roles?

DNA stores the long-term genetic instructions, while RNA copies and carries those instructions to guide the building of proteins.

What is the genetic code?

It is the set of rules by which groups of three DNA or RNA bases specify particular amino acids, allowing genes to direct protein assembly.