Foundations

What is a gene?

A gene is a DNA region that produces a functional RNA product; some genes also encode a protein. The genome includes all genetic material, including non-coding and regulatory DNA. The human haploid nuclear genome contains about 3.1 billion base pairs and roughly 20,000 protein-coding genes.

Key points

  • Most nucleated body cells contain 46 chromosomes and many DNA regions with different functions.
  • Around 20,000 protein-coding genes make up less than 2 percent of the genome.
  • Many genes produce functional RNAs; some of these serve as templates for proteins.
FROM CELL TO GENECellNucleusChromosomeDNAGeneEvery cell carries the same DNA; a gene is one section on the strand.

From the cell to the gene

Most nucleated body cells contain nearly the same genetic information in their nuclei; mature red blood cells, for example, have no nucleus. The nuclear genome is organised into chromosomes, with DNA packaged around proteins. A gene includes the regions needed to produce a functional RNA and may include regulatory regions.

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

Protein-coding regions make up only a small part of the genome. Other regions include genes for functional RNAs, regulatory sequences and DNA whose function is not fully understood. Not every functional DNA sequence is considered a gene; the term depends on a clear biological definition. Genomic analysis also needs a defined reference and 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

DNA: bases and double helixChromosomes and karyotypeGene structure: exon, intron, promoterFrom gene to proteinrsIDs, microarray and SNP lookup

Sources

  1. 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
  2. 2Nurk et al., 2022 The complete sequence of a human genome (T2T-CHM13). Science 376:44-53. doi.org/10.1126/science.abj6987