"When most biologists hear the name Lamarck or the term soft inheritance, the reaction is, 'Oh my God, here we go again'," Richards says. "But from a molecular biology point of view there is a mechanism to do soft inheritance, and epigenetic inheritance can be construed as a form soft inheritance. That's all I'm saying. The really heretical thing to say is that the environment could be pushing the epigenetic information in a direction that is beneficial. This is the more extreme variation of soft inheritance that raises the hackles."
Epigenetic mechanisms leave DNA sequence unaltered but can affect DNA by preventing the expression of genes. Richards cites a study that shows certain epigenetic alleles can be inherited that affect tumor suppressor genes. His own work in plants has often shown epigenetic information can be inherited. The Richards lab specializes in epigenetics, a biological field that deals with information stored "above and beyond the gene," referring to the Greek meaning of the term. A classic epigenetic mechanism is a process known as DNA methylation, a chemical modification of cytosine, one of the four chemical subunits of DNA. Without proper DNA methylation, higher organisms from plants to humans have a host of developmental problems, from dwarfing in plants to certain death in mice.
The next level of gene regulation studied in epigenetics is DNA packaging. DNA is wrapped around proteins similar to the way that thread is wrapped around a spool. Loosely wrapped DNA is more readily accessible and therefore more easily expressed than tightly wrapped DNA, allowing another mechanism for regulation of gene expression. The location of DNA within the nucleus also influences gene expression.
"Epigenetics as soft inheritance in mammals puts us on a slippery slope that many people don't want to visit," Richards says. <
Source:Washington University in St. Louis