Individuals are different: they vary in the genes they possess (their genotype) and in the physical characteristics they acquire as the result of the interactions between their genes and environmental factors (their phenotype).
Variations in the genotype may be due to:
- changes in the nucleotide sequence within a gene (gene mutations)
- large alterations in the structure of chromosomes
- changes in the total number of chromosomes
Geneticists study the way in which genes (and their associated characteristics) are passed from generation to generation by examining patterns of inheritance.
Population genetics is the study of the variations in the genes found within groups of individuals.