The term was first coined by Alexander Brink in 1950 and was further observed in maize plants in the1960s. At first, it was believed to be a constraint on gene expression during an individual's development caused by different factors in the chromosome . It was later determined that it is an epigenetic transfer of information from one allele of a gene to another that leads to a heritable state of gene expression.
Three key features of a paramutation include: (1) heritable
(2) The altered locus issues similar intructions to homologous sequences (3) The DNA sequences do not change but there is a different methylation pattern.
Commonly, the b1 locus in maize is used to demonstrate this phenomenom. This locus encodes a transcription factor that promotes the synthesis of a purple pigment. The B-1 allele has a higher expression of b1 so it is therefore purple. However, the B' allele is weakly transcribed and is therefore a light pigment. Both the the B' and b1 allele sequences are the same but the difference is in the methylation pattern and the chromatin .
1. Brink, R. ALexander, E. Derek, Styles and John D. Axtell. "Paramutation:Directed Genetic Change Paramutation occurs in somatic cell and heritability alters the functional state of a locus." Science. 159.3811 (1968): 161-70.
2. Chandler, Vicki. Paramutation: From Maize to Mice. Cell. 128.4 (2007): 641-645