Genetic instability

Genetic imprinting is a phenomenon in mammals where the gene's expression is determined by the parent that contributed it. This process is an exception to the usual rules of Mendelian inheritance, which state that both alleles in a gene pair have an equal chance of being expressed.

Overview

Genetic imprinting involves the silencing of a gene by the addition of a methyl group to its DNA. This process, known as DNA methylation, prevents the gene from being transcribed into RNA and thus from being expressed. The silenced gene is said to be "imprinted," and this imprint is maintained during the cell's DNA replication and cell division processes.

Mechanism

The mechanism of genetic imprinting is complex and not fully understood. It is known to involve DNA methylation and histone modification, two processes that alter the structure of DNA and chromatin, respectively, without changing the underlying genetic sequence. These changes can affect how genes are expressed.

Clinical significance

Abnormalities in genetic imprinting can lead to a number of diseases, including Prader-Willi syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome. These conditions are characterized by a variety of physical and mental abnormalities, and are often associated with a high risk of cancer.

See also

• Epigenetics
• Genomic imprinting in plants
• Parental imprinting