Aging

Aging
Definition
The process in which cells start deterioration in their structure and function and tissues of the body become older is called Aging.
OR
Negative physiological changes in the body of multicellular organism is called Aging.
Gerontology
The science which deals with the study of aging is called Gerontology.
Sign of Aging
The following signs of old age may usually be observed.

• Loss of hair pigmentation
• Skin wrinkled
• Development of small pigmented area in the skin of face and arms.
• Loss of memory
• Fat deposition increases
• Vision become poor
• Body become weak
• Decreased body immunity
• Degenerative diseases appears
• Pain in joints

Causes of Aging
There are many causes of aging, but two causes are very important
1. Genetic Origin
2. Gene Mutation
1. Genetic Origin
According to scientist Hayflick and Paul head cells of body can divide for a limited period. The cells undergo mitosis certain times. When cells do not work properly, cell division decreased, the body become affected. It is the main cause of aging and cell start die.
2. Gene Mutation
Due to certain reasons changes in the genes and DNA replication is affected. This is called mutation. Some substances damage the DNA and function of cell become less / weak, it causes aging.
Using Measures to Decrease Aging
Low fat diet, low impact exercises, aerobic are the factors which reduced aging.
Cell Differentiation
Definition
The cell of selection of activation of some genes by a cell (which are not activated by the other cells of the embryo) is called cell differentiation.
Experiment
John Gurdon removed the nucleus from the unfertilized egg of frog. Then he obtained nucleus from intestinal cell of a tadpole of the same species and implanted it into the enucleated egg. This egg with this new nucleus, developed into a complete frog. It indicates that there is no change in the genetic information of separated cell of any other part and it is active according to the genes.
Example
Only in immature R.B.C the genes become active to form haemoglobin, so it indicates the process of cell differentiation.
Mechanism of Differentiation

• During the differentiation process, the genetic expression is influenced by the cytoplasmic chemical composition.
• Different properties of cytoplasm in the unfertilized ovum is responsible for later differentiation of embryonic cells into tissues.
• When cleavage occur in zygote, the cytoplasm is also divided.
• Each dividing cell contain all necessary material like protein, mRNA and other molecule.
• With the help of these substance cell are changed into different tissues.