Most biological traits are under the influence of polygenes (many different genes) as well as gene–environment interactions. Genotypes along with environmental and developmental factors determine what the phenotypes will be. These genes make up different DNA sequences called genotypes. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits.

This is an exception to the strict definition of a gene described above.)

(Some viruses have an RNA genome so the genes are made of RNA that may function directly without being copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. ĭuring gene expression, the DNA is first copied into RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. The Mendelian gene is a basic unit of heredity and the molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. In biology, the word gene (from Greek: γένος, génos meaning generation or birth or gender) can have several different meanings. A human chromosome can have up to 500 million base pairs of DNA with thousands of genes. A chromosome consists of a long strand of DNA containing many genes.

A gene is a region of DNA that encodes function.

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