EPIGENETICS Controlling Genes from Within

Epigenetics  Literally means “above the genome”  Chemical “tags” present ON gene can switch gene “ON” or “OFF” which alters “expression” Ex: Methylation (adding CH 4 or methane) to DNA or Phosphorylation (adding PO 4 or phosphate) to a gene AGTCAAACCCGGGTTT TACGTACGTACGTACG CH 4

Two genetically identical mice with “agouti” fur color gene. Yellow mouse’s gene is turned “ON” while brown mouse’s gene is turned “OFF.” Turning on gene makes mouse’s appetite insatiable causing it to eat itself to obesity, diabetes, cancer, and death. Methyl (CH 4 ) turns off agouti gene.

 DNA is packaged in cells in systematic way  1. twisted into double helix  2. coiled around proteins called histones (DNA now called nucleosomes)  3. further coiling together (DNA now called chromatin)  4. coiled into chromosome

DNA Packaging

 Chemical tags alter gene expression either by:  CH 4 attaching directly to DNA turns off gene  Any chemical attaching to protein histone which then “hides” gene Tags make DNA wrap tighter or looser, which can hide gene segment from being transcribed (no mRNA made)

green In the cell, DNA is wrapped around proteins called histones, shown here in green. When the histones squeeze the DNA tightly, they "hide" that gene from the cell.

 Environmental factors can alter epigenome of human  Smoking  Alcohol  Diet/food intake  Stress  Radiation  Pesticides  ???

Skin that has been repeatedly exposed to the sun looks older than skin that hasn't because the skin's stem cells have had to divide more often to repair damage.

 As we age, more and more chemical tags get added to the genes, so the accumulation is seen over time. Epigenetic damage (seen here in more widespread darker areas) accumulates as we age. The DNA on the left is from an eight-year-old, while the corresponding stretch of DNA on the right is from a 60-year-old. 8 60

 Environment of nurture can determine fate of child/grandchild  Famine  Depression/mental disorders  Diabetes  Drug use  Blood pressure  Poverty

American Poverty and Development  In 2008, data was collected from Cleveland High on its special education population  More African-Americans and Latinos are classified as “special ed” than any other ethnic group (10.5% African-American, 9.5% Latino)  Across the country, statistics are the same

 What is happening in the African-American and Latino communities? What do they have in common?  Poverty – both ethnicities have higher incidences of poverty than any other groups Diet: people tend to have poorer diets (higher in fat, lower in vegetables) Exercise: children have little access to organized sports (money), may have to stay home to take care of siblings, live in gang-infested areas (can’t play outside) Health: children have higher incidences of disease, which can lead to missed school, lack of education (cycle continues) Stress: increase of stress hormones leads to heart disease, obesity (shorter life span)

 Might children who were impoverished pass down epigenomic factors to their grandchildren?  Males: poverty during puberty affects development of DNA in sperm, which affects offspring  Females: poverty of mothers while pregnant affects development of DNA in eggs, which affects offspring Can we EVER get away from devastating effects of poverty?

MOVIE: Ghost in Your Genes  Pay attention – this is critical to you learning the content and critical for your test on Monday.