A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic.

A gene occupies a specific position on a chromosome.

The various specific forms of a gene are alleles.

Alleles differ from each other by one or only a few bases.

New alleles are formed by mutation.

The genome is the whole of the genetic information of an organism.

The entire base sequence of human genes was sequenced in the Human Genome Project.

Application: The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin.

Application: Comparison of the number of genes in humans with other species.

Skill: Use of a database to determine differences in the base sequence of a gene in two species.