What is a gene?
A gene is a stretch of DNA that carries the instructions for a product, usually a protein. The DNA sits coiled inside the chromosomes in the cell nucleus, and the sum of these stretches is the genome. Humans have around 20,000 protein-coding genes spread across roughly 3.1 billion base pairs.
From the cell to the gene
Almost every cell of the body carries the same complete blueprint in its nucleus. It sits in 46 chromosomes, and each chromosome is a single, very long DNA double strand wound tightly around proteins. A gene is a delimited section on this strand. Unrolled, the DNA of one cell would measure about two metres.
What a gene does
Most genes carry the instructions for a protein, the actual working material of the cell. The gene is read out and transcribed into a messenger RNA, which then serves as the template for building the protein. Other genes yield functional RNA that never becomes protein. What a gene does depends on its sequence, that is the order of its bases.
How many genes, and what lies between them
The protein-coding genes fill only a small part of the genome. The far larger remainder consists of regulatory sections, RNA genes, structural elements and sequences with no known function. That is why the term gene has softened: it once meant a protein recipe, today it means any section with demonstrable function. For Genome what matters above all is which base sits at which position.
What Genome measures. Genome reads genotypes at defined positions inside genes. Each gene article in the wiki names which position of which gene is meant and what it says.
Related topics
Sources
- 1Gerstein et al., 2007 What is a gene, post-ENCODE? History and updated definition. Genome Research 17:669–681. doi.org/10.1101/gr.6339607
- 2Nurk et al., 2022 The complete sequence of a human genome (T2T-CHM13). Science 376:44–53. doi.org/10.1126/science.abj6987