Biology

Biology
Part I:
For this activity, you will need to watch three short videos. The links to these videos can be found on your Blackboard site under the folder heading “Lab: Epigenetics.”
The Epigenome at a Glance:  http://learn.genetics.utah.edu/content/epigenetics/intro/
Insights from Identical Twins: http://learn.genetics.utah.edu/content/epigenetics/twins/
A Tale of Two Mice: http://www.pbs.org/wgbh/nova/body/epigenetic-mice.html

1.    Explain how two genetically identical twins could potentially not be identical.

2.    In what way do the brown and yellow mice shown in the Tale of Two Mice video differ? Why is this so?

3.    Explain DNA methylation. How does this process influence cellular function?

4.    Describe the role of histone proteins within a chromosome.

5.    Summarize in your own words how epigenetic modification affects DNA structure and function.

Part II: Below are the experimental results published in Figures 4 and 5 of the Environmental Health Perspectives article Maternal Genistein Alters Coat Color and Protects Avy Mouse Offspring from Obesity by Modifying the Fetal Epigenome. In this study, pregnant mice were exposed to genistein, a component of soy, to determine if exposure to genistein influenced gene expression among genetically identical offspring.

Mouse Coat Color    % Methylation in Tail Tissue (T) on day 21    Body weight (g) at week 60
(see figure 4)    (see figure 5)
Yellow
Slightly Mottled
Mottled
Heavily Mottled
Pseudo-agouti (brown)

1.    According to Figure 4, what is the relationship between percent methylation (y-axis) and coat color (x-axis)?

2.    According to Figure 5, what is the relationship between body weight (y-axis) and coat color (x-axis)?

3.    What explains the five different coat colors observed among offspring?

4.    In which mouse population is the Agouti gene silenced?

5.    In which mouse population is the Agouti gene silenced?

6.    Read the authors’ conclusions below. After reading the author’s conclusions write a 4-5 sentence paragraph disussing how these conclusions could be relevant for humans.

“In the present study, we observed a statistically significant shift in coat-color phenotype and adult body weight distribution among genetically identical offspring whose mothers received a diet supplemented with 250 mg/kg diet of genistein. The shifts in coat color and body weight were mediated by increased methylation … of the Agouti gene. Hypermethylation in the genistein-supplemented population results in decreased ectopic Agouti expression, which reduces yellow phaeomelanin production and protects against adult-onset obesity. This is the first study to demonstrate that exposure to dietary genistein in utero, at levels present in human adult populations consuming high-soy diets, affects coat color and reduces population incidence of obesity by altering the epigenome in mice. Thus, an active ingredient in soy enhances the early establishment of DNA methylation.… [O]ur findings show that early nutritional and environmentally induced epigenetic modifications can provide an alternative mechanism for varying individual susceptibilities to environmental agents. Our results also suggest a plausible explanation for the lower incidence of certain cancers in Asians compared with Westerners (Chang et al. 2001; Lee et al. 1991) as well as the increased cancer incidence in Asians who immigrate to the United States (Ziegler et al. 1993).”TT