Epigenetics

1. Epigenetics Why are some genes expressed and not others?

2. WHAT IS EPIGENETICS? “The development and maintenance of an organism is orchestrated by a set of chemical reactions that switch parts of the genome off and on at strategic times and locations.” “Epigenetics is the study of these reactions and the factors that influence them.” From http://teach.genetics.utah.edu/

3. DNA wrapped around histones with methyl (green) and acetyl (red) groups controlling how tightly they are wrapped

4. So How Does this Work Chemically?

5. What should you be able to do? Describe the physical state of the genome (tightly wrapped, or relaxed) when genes are inactive. Describe the physical state of the genome when genes are active.

6. The epigenome marks your genome in two ways, both which may turn genes off or on. • The first type of mark, called DNA methylation, directly affects the DNA in your genome. This can also occur with acetylation. • In this process, chemical tags called methyl groups attach to the backbone of the DNA molecule in specific places. • The methyl groups turn genes off or on by affecting interactions between DNA and the cell's protein-making machinery. • http://www.genome.gov/27532724

7. The second kind of mark, called histone modification, indirectly affects the DNA in your genome. • Histones are proteins which enable DNA's molecules to be wound up neatly into chromosomes inside the cell nucleus. • A variety of chemical tags can grab hold of the tails of histones, changing how tightly or loosely they package DNA. • If the wrapping is tight, a gene may be hidden from the cell's protein-making machinery, and the gene may be switched off. • In contrast, if the wrapping is loose, a gene that was formerly hidden may be turned on.

8. So who would make a good model for epigenetics? How about identical twins?