Editing Genetic variation (section)

== Among individuals within a population ==

Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of [[phenotype|phenotypic]] variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color in certain flowers).{{cn|date=December 2021}}

Genetic variation can also be identified by examining variation at the level of enzymes using the process of protein electrophoresis.<ref>{{Cite web|url=https://www.yourgenome.org/facts/what-is-gel-electrophoresis|title=What is gel electrophoresis?}}</ref>  Polymorphic genes have more than one allele at each locus.  Half of the genes that code for enzymes in insects and plants may be polymorphic, whereas polymorphisms are less common among vertebrates.{{cn|date=December 2021}}

Ultimately, genetic variation is caused by variation in the order of bases in the [[nucleotide]]s in genes. New technology now allows scientists to directly sequence DNA, which has identified even more genetic variation than was previously detected by protein electrophoresis. Examination of DNA has shown genetic variation in both coding regions and in the noncoding intron region of genes.{{cn|date=December 2021}}

Genetic variation will result in phenotypic variation if variation in the order of nucleotides in the [[DNA sequence]] results in a difference in the order of [[amino acid]]s in proteins coded by that DNA sequence, and if the resultant differences in [[Peptide sequence|amino-acid sequence]] influence the shape, and thus the function of the enzyme.<ref>{{cite journal|last1=Pavlopoulos|first1=GA|last2=Oulas|first2=A|last3=Iacucci|first3=E|last4=Sifrim|first4=A|last5=Moreau|first5=Y|last6=Schneider|first6=R|last7=Aerts|first7=J|last8=Iliopoulos|first8=I|title=Unraveling genomic variation from next generation sequencing data.|journal=BioData Mining|date=25 July 2013|volume=6|issue=1|pages=13|doi=10.1186/1756-0381-6-13|pmid=23885890|pmc=3726446 |doi-access=free }}</ref>