3 December 2014
1. The epigenome shapes the physical structure of the genome. It tightly wraps inactive genes, making them unreadable. It relaxes active genes, making them easily accessible. Different sets of genes are active in different cell types. 2. Yes, as cells grow and divide, cellular machinery faithfully copies epigenetic tags along with the DNA. Using the original DNA strands as a template, methyl copying enzymes attach methyl tags to newly replicated DNA copies. One original DNA strand and one copy will be passed to each daughter cell. 3. As twins age their environments begin to differ. Their genomes remain the same, but signals from the environment act on the twins’ epigenome to activate and silence different genes, making them increasingly different. 4. Environmental factors include: die, differences in physical activity, exposure to toxins, stress, and etc. 5. The nurturing behaviour of a mother rat during the first week of life shapes her pups' epigenomes. A high nurturing mother rat shapes her pup’s epigenome by licking, grooming, nipple switching, and arched back nursing. Highly nurtured rat pups tend to grow up to be calm, relaxed adults, while rat pups who receive little nurturing tend to grow up to be anxious and aggressive. The anxious, guarded behaviour of the low-nurtured rat is an advantage in an environment where food is scarce and danger is high. The low nurtured rat is more likely to keep a low profile and respond quickly to stress. In the same environment, a relaxed rat might be a little too relaxed. It may be more likely to let down its guard and be eaten by a predator. [see http://learn.genetics.utah.edu/content/epigenetics/rats/] 6. In rats, licking by the mother deactivates her pup’s GR gene. Rats (and people) with higher levels of GR are better at detecting cortisol, and they recover from stress more quickly. [Diagram explaining to the right] 7. When mothers do not nurture...
Please join StudyMode to read the full document