Thus we know that as twins age epigenetic differences accumulate especially

Thus we know that as twins age epigenetic differences

This preview shows page 59 - 61 out of 87 pages.

Thus, we know that as twins age, epigenetic differences accumulate, especially when lifestyles differ. Our epigenomes are influences by what we eat, what we drink, what we smoke, etc. How does this explain Rainbow and CC? This is also hugely important for understanding health. As epigenomes change over time, virtually altering the work of our genes, cells can become abnormal, triggering diseases like cancer. Given this knowledge: we now have epigenetic therapies (some): we have some drugs that can re-activate genes, i.e., alter the existing epigenetic tags to change the existing bad cells rather than destroying them. There has been some success with these methods for treating some diseases (e.g., MDS, a form of blood cancer). Summary: We can’t change our genome but we CAN alter out epigenome. And, this is important not only to us and the children we bear but to future generations because epigenetic instructions are passed on to future generations! Prenatal Development Gestation = 266 days from conception, + 1 week 280 days from beg. of last menstrual period, + 1 week (so, about 40 weeks) physicians/patients usually use menstrual age although conceptual age is a better predictor, or more accurate measure, of fetal development Germinal Period/Period of Zygote (0-2 weeks) 1. zygote = newly fertilized egg 2. major developments: a. ongoing cell division (mitosis) b. migration c. implantation d. beginning of differentiation 3. almost immediately after fertilization, the zygote begins the process of cell division a. however, it takes almost 30 hours until the original zygote divides into 2 daughter cells b. mitosis moves along, picking up speed c. by about day 5, the zygote becomes a mass/ball of approx. 100 undifferentiated cells, known as a blastocyst , with 2 layers: 1) inner layer of cells makes up the embryonic disk , which will develop into the new organism 2) outer layer of cells make up the trophoblast , which will develop into a support system which will nourish & protect the developing organism
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4. migration -- zygote takes about 3 days to move through the Fallopian tube into the uterus, where it floats freely for another four or five days before implanting itself in the nutrient-rich uterine wall 5. implantation occurs between days 7 and 9 a. zygote attaches itself to the uterine wall b. to survive, the zygote has to implant itself in the right place at the right time 1) could implant itself in the wrong place (e.g., tubal pregnancy) 2) could wait too long to implant, then the uterus is no longer receptive to implantation 3) could fail to implant altogether (approx. 30% of fertilized ova will fail to implant) Differentiation -- by the end of the 2 weeks, the cells have multiplied greatly in number and have begun to differentiate themselves Cells differentiate not only into different parts of the developing organism, but also other important structures as well Blastocyst Cells (will become organism but some become): a. Amnion = inner membrane of sac (Amniotic Sac) 1) amniotic sac contains the developing organism within a liquid environment (amniotic fluid)
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