Summary
A segment of DNA that carries the instructions for making a particular protein or RNA.
In depth
Genes are units of heredity located at fixed positions (loci) on chromosomes. A typical human gene has exons and introns, regulatory regions such as promoters, and gives a protein or a functional RNA. Humans have about 20,000 protein-coding genes covering only around 1.5 percent of the genome.
Genes differ greatly in size; dystrophin is over 2 million base pairs.
Key idea: a gene is best defined by function: a DNA sequence that produces a functional product.
The classic idea of one gene, one enzyme (Beadle and Tatum, 1941) has been refined: one gene can produce several protein variants through alternative splicing, and some genes make only RNA. The human genome holds about 20,000 protein-coding genes covering only around 1 to 2 percent of the DNA, with many more regulatory and non-coding regions.
A gene has a promoter, coding regions (exons), non-coding intervening regions (introns), and control elements such as enhancers that can lie far away. Gene sizes vary: the dystrophin gene spans over 2 million base pairs.
Remember: a gene is a stretch of DNA with a function, not the trait itself; traits usually involve many genes and the environment.
Frequently asked questions
What is Gene?
A segment of DNA that carries the instructions for making a particular protein or RNA.
Which area of biology covers Gene, and how advanced is it?
Gene is one of the 54 topics in Genetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Genetic Linkage Mapping, Heredity, Polygenic Inheritance.
What should I learn before Gene?
Gene is a Beginner topic, so no earlier topic is required. Other Beginner topics in Genetics that pair well with it include Heredity, Allele, Genotype and Phenotype.
What topics are related to Gene?
The closest topics to Gene are Genetic Linkage Mapping, Heredity, Polygenic Inheritance, Allele. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Gene?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Gene. To practise the whole of Genetics, use the Genetics quiz.
How is Gene different from Genetic Linkage Mapping?
Gene: A segment of DNA that carries the instructions for making a particular protein or RNA. Genetic Linkage Mapping: Uses recombination frequencies between genes to build maps measured in centimorgans. Read both side by side and note what each one explains.
How should I study Gene step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Genetic Linkage Mapping and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.