Gene
Genetics · Molecular Biology · Genomics
Say it: JEEN
A gene is a stretch of DNA that carries the instructions for making a protein or a working RNA molecule, and is the basic unit of heredity.
Also: genes
Definition
What is a gene?
A gene is the basic unit of heredity: a segment of DNA, passed from parents to offspring, that holds the information for making a particular product. Most genes code for proteins, but some code for RNA molecules that do their jobs without being translated, such as transfer and ribosomal RNA, and other stretches of DNA control when genes are switched on. Humans have roughly 20,000 protein-coding genes, which take up only a small fraction of the genome, and a single gene can be anywhere from a few hundred to more than two million base pairs long.
To be used, a gene is first transcribed into RNA, and the message of a protein-coding gene is then translated into a chain of amino acids. In eukaryotes, many genes are split into exons, which are kept, and introns, which are removed. A person usually carries two copies of each gene on the autosomes, one from each parent, and slightly different versions of the same gene are called alleles.
The word was coined by the Danish botanist Wilhelm Johannsen in 1909. Genes have official names and short symbols, such as CFTR for the gene involved in cystic fibrosis.
Word parts
Where does the word “gene” come from?
- gen-
- birth, descent, generationGreek genea, genos
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Related
Terms that go with it
- AlleleAn allele is any of the alternative forms of a gene or DNA sequence that can occupy the same position, or locus, on a chromosome.
- DNADNA is the double-stranded molecule that carries the genetic instructions of nearly all living things, written in a code of four bases: A, T, C and G.
- GenomeA genome is the complete set of DNA in an organism or cell, including all of its genes and the stretches of DNA between them.
- Gene expressionGene expression is the use of a gene's information to make a working product, usually a protein or a functional RNA molecule.
- ChromosomeA chromosome is a thread-like structure of DNA and protein that carries an organism's genes; most human cells hold 46 of them in 23 pairs.
- ExonAn exon is a section of a gene that stays in the final RNA after splicing removes the introns, and most exons carry code for protein.
Sources
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