The cells began to divide.


The cells began to divide.

How many human cells die daily?
For adults it셲 about 50-70 billion per day. Surprising? Worried?
The human body is made up of trillions of cells.
And cells create and divide cells.
All cells need a constant production of energy to maintain their genetically programmed function.

Cell division is the process by which a parent cell divides into two or more daughter cells.

Cell division usually occurs as part of a larger cell cycle.
When young, we are making many more new cells than we lose existing cells, and when aging, or when we get sick, we are losing more cells than we are making new cells to replace them.
There쨈s a difference between individuals.
Many specialists say, 쏛ging can slow down how to manage a body. 짤 2015. All rights reserved


from INSTANT EXPERT 29 in Magazine New Scientist 2013, Jan 5

Solving the mystery


We started to get the first glimpses of some of the mechanisms involved in epigenetic phenomena in the 1970s and 1980s. Most turned out to entail chemical changes to either DNA itself, or its packaging proteins. Some of these chemical marks or tags promote gene activity that is, allow a gene셲 protein to be manufactured while others
have the opposite effect, shutting a gene down.
The primary means of controlling gene activity is thought to be through transcription factors, proteins that bind
to a stretch of DNA next to a gene, known as its control region, to turn it on or off. Epigenetic changes seem to complement the activity of transcription factors.
The first example discovered was DNA methylation, which involves a small chemical subunit called a methyl group
being added to DNA. The 쐋etters of the DNA code were known to consist of four types of base: adenine, cytosine, guanine and thymine. We셝 known for decades that DNA also contains small amounts of a fifth base, methylated cytosine but only in the late 1970s did it become possible to map where in the genome this modified base appeared.
A striking pattern emerged: DNA methylation is dotted around over most of the genome, but is usually conspicuously absent from gene control regions. Crucially, when the control region is methylated, the gene cannot be turned on and is said to be silenced.
Methylation of a gene셲 control regions is used, for example, to silence one female X chromosome and to ensure that genes involved in the making of sperm and eggs are switched off in the rest of the body. Importantly, patterns of DNA methylation are copied when DNA is replicated and are therefore passed on from a mother cell to its daughters as the cell divides. This cell-to-cell heritability helps explain why epigenetic gene silencing is so stable over time.

Related Articles