Epigenetics

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 * 1) Epigenetic changes not only influence the expression of genes in plants and animals but also enable the differentiation of pluripotent stem cells (cells having the potential to become any of many different kinds of cells). (70)
 * 2) Epigenetic modifications can define how the information in genes is expressed and used by cells. (62)
 * 3) Similarly, specific histone modifications may distinguish actively expressed genes from genes that are poised for expression or genes that are repressed in different kinds of cells. (58)
 * 4) In other words, epigenetic changes allow cells that all share the same DNA and are ultimately derived from one fertilized egg to become specialized—for example, as liver cells, brain cells, or skin cells. (55)
 * 5) The term epigenetics came into general use in the early 1940s, when British embryologist Conrad Waddington used it to describe the interactions between genes and gene products, which direct development and give rise to an organism’s phenotype (observable characteristics). (49)

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What Makes a Stem Cell Pluripotent?
To understand how a cell becomes pluripotent, it helps to consider the human body in the very early stages of development. After an egg is fertilised by a sperm, a single cell results. This cell - the fertilised egg that is totipotent - has the potential to create an entire organism. In the initial hours and days following fertilisation, this single totipotent cell divides into more totipotent cells that are exact copies of the original.

Approximately four days after fertilisation, the totipotent cells start to specialise and form a cluster of cells known as a blastocyst. The blastocyst has yet another smaller group of cells known as the inner cell mass and it is these inner pluripotent stem cells that will go on to create most of the cells and tissues in the human body. These pluripotent stem cells are therefore different than totipotent stem cells because they don't develop into a complete organism. As such, a pluripotent cell won't give rise to the placenta or other tissues that are vital for foetal development. It will still develop into the other specialised cell types in the human body, such as nerve or heart cells.

You may have also heard the term 'stem cell line.' Stem cells from embryos can be used to create these pluripotent stem cell 'lines,' which are grown in the laboratory or cultured from foetal tissue.

[|Case Studies]1. Restoring Eyesight After Chemical Burns, 2. [|Stem Cell Scandal: A Case Study]

**Epigenetics**: Definition & Examples - LiveScience.com
www.livescience.com/37703-**epigenetics**.html Cached Jun 24, 2013 · **Epigenetics** refers to external modifications to DNA that turn genes "on" or "off." These modifications do not change the DNA sequence.

**Epigenetics**? - What is **Epigenetics**? - Epigenome NOE
www.epigenome.eu/en/1,1,0 Cached What is **Epigenetics**? Conrad Waddington (1905-1975) is often credited with coining the term **epigenetics** in 1942 as “the branch of biology which studies the ...

**Epigenetics** - Learn Genetics
learn.genetics.utah.edu/content/**epigenetics** Cached **Epigenetics** is the study of these chemical reactions and the factors that influence them. introductory video. The Epigenome at a Glance Meet the epigenome and ...

NOVA | **Epigenetics** - PBS
www.pbs.org/wgbh/nova/body/**epigenetics**.html Cached **Epigenetics** Produced, Directed and Edited by Sarah Holt NOVA scienceNOW Executive Producer Samuel Fine Executive Editor Neil deGrasse Tyson Senior Series Producer

**epigenetics** -- Encyclopedia Britannica
www.britannica.com/EBchecked/topic/1372811 Cached **epigenetics**, the study of the chemical modification of specific g