Gene

Genes

Gene expression

The structure of a eukaryotic protein-coding gene.

Gene

A gene is a distinct sequence of nucleotides that form part of DNA. It carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses. Genes guide each aspect of an organism's cellular processes by encoding essential proteins and molecular structures.

Definition

Historically, a gene was described as:

1. A hereditary unit occupying a specific position or locus on a chromosome.
2. A unit influencing one or more specific effects on the phenotype of an organism.
3. A mutable unit capable of presenting various alleles.
4. A unit capable of recombining with other such units.

Modern understanding has expanded on this original concept, revealing two primary classes of genes:

1. Those transcribed into RNAs and subsequently translated into polypeptide chains.
2. Genes producing transcripts (e.g., tRNAs, rRNAs, snRNAs) utilized directly, such as operators that function as 'regulatory sequences' during DNA's transcription and translation.

Structure and Function

Genes possess intricate structures beyond mere protein-coding sequences. The DNA regions that aren't transcribed and untranslated sections of the RNA are crucial components of a gene's architecture.

Function of Genes

Genes dictate the physiological and physical attributes of organisms, including humans. They define our appearance attributes such as skin, hair, and eye color. Furthermore, genes determine numerous biological processes and are responsible for various genetic effects within our bodies.

Inheritance

Genes transfer from parent to offspring, determining various biological traits of the child. Half of an individual's genes derive from the mother and the other half from the father. The manifestation of these inherited genes can be either dominant or recessive, terms that denote a gene's influence when present in an offspring's genome.

Significance in Humans

Humans possess approximately 20,000 protein-coding genes, with numerous others being non-coding. These genes hold the chemical information necessary for creating every protein a cell requires throughout its lifetime.

Also see

• Glossary of genetics

Related pages

• Allele#Dominance
• Sequence analysis
• Genetics
• ENCODE, the complete analysis of the human genome
• Gene therapy