Novel genetic and epigenetic alterations in ... - Ous-research.no

GENERAL INTRODUCTIONGenetic and epigenetic inheritance“Genetic inheritance is the biological process wherebygenetic factors are transmitted from one generation tothe next”The principles behind genetic inheritance was elegantly described by Gregor Mendelin the mid 19 th century, where he showed that an offspring inherit one allele ofeach gene from each of its parents, and that the encoded information from thesemake out the phenotype[4]. Although it took 34 years until his work was re-discovered andappreciated, the Mendelian heritage has ever since been widely accepted as the default way ofgenetic inheritance. The fact that DNA is the crucial compound of this inheritance was notshown until 1952, almost a century later[5], a year before the DNA structure itself wasresolved[6]. Since then, the knowledge of inheritance has exploded. Some features are nowknown to be inherited in a non-mendelian manner, i.e. not according to Mendel’s laws ofinheritance. We also know that it is possible that information which is not coded by theDNA sequence itself can be passed to the next generation.This exception from the Hershey and Chase findings in 1952 is called epigenetics. There aretwo kinds of epigenetic inheritance; cellular/somatic, the one from a cell to its daughter cells;and transgenerational/germline, from one parent to its offspring, the latter a recent anddebated finding[7]. When epigenetic information is passed from a mother cell to its daughtercells, methylation marks are kept on the initial DNA strand during replication and celldivision, causing the epigenetic pattern to be re-established in the daughter cell[8].11