Estimation and Regulation of DNA:
The Future Tool for Diagnosis, Treatment and Prognostic Evaluation of Cancer
- Part 1 -

JC Sanasam *

...Cells in the body have different shapes and sizes, and are capable of changing according to time and situation. Fat cells are globular while nerve cells have long branching axons for transmitting messages...

Most people have heard about DNA but many of us are still vague about what it is. Here is a brief account.

Cells are the smallest structural units in the body, and are grouped into different types of tissue. All types of cell have a similar internal structure regardless of their function, and most cells at their centres have a nucleus, the cell's control centre, that contains a substance called DNA, which carries the gene information that is passed from parent to child.

DNA controls not only the distinguishing features, but also the way in which individual cells function. The DNA exists admixed in a protein material called the chromosomes in the cell nucleus. Most cells contain a complete set of genetic instructions, but within each cell only those needed for its particular function are activated.

For example, instructions for making the hormone insulin are present in the DNA of every cell in the body, but this instruction is used in or followed by the cells in the pancreas (an organ near the stomach and liver) only. Cells in the body have different shapes and sizes, and are capable of changing according to time and situation.

Fat cells are globular while nerve cells have long branching axons for transmitting messages. White blood cells can become long and thin to squeeze through tiny capillaries, or send out 'arms' to grab and engulf invading enemies, the microorganisms.

Cells keep dividing forming into new cells and old cells die out. Chromosomes, that contain the DNA are threadlike structures found in the cell nucleus. Each chromosome consists of a giant molecule of DNA coiled round a protein core. Each bundle of chromosome replicates itself, forming two identical versions that link up in an X shape.

As the cell divides, each pair of chromosomes splits apart and one copy is drawn into each new cell. Not long after the new cells separate, the bundled chromosomes unravel again.

All human cells within a nucleus have 46 chromosomes, apart from the sperm cells in males and egg cells in females, which have 23. The 46 chromosomes in nonsex cells are copies of the 23 from the mother's egg and the 23 from the father's sperm. Males have XY type of chromosomes and females XX type.

The chromosomes in every sex cell are unique, so brothers or sisters are never completely alike. Identical twins look the same because they develop from one egg that splits in two after fertilization, the point at which the two sets of parental chromosomes amalgamate in one nucleus.

The term DNA stands for deoxyribonucleic acid, the name of its chemical composition and structure that exists in all living organisms (and can survive in their remains for thousands of years after death). It carries all the information a cell requires to make the proteins that it needs to function.

Four bases called adenine (A), thymine (T), guanine (G) and cytosine (C) in pairs are present in each DNA. They always pair in the same combinations - adenine to thymine and guanine to cytosine. The order in which the four chemical bases occur along the length of the molecule provides the genetic code. In order to duplicate itself prior to cell division, a DNA molecule splits along its length and each side reproduces the missing half, replicating the entire sequence for use in the new cell.

A gene is a segment of DNA containing the instructions for the formation of one particular protein. The term is also used describe a section of DNA that determines a specific physical characteristic, such as blue eyes in certain individuals in the family of a race; or function, such as normal or abnormal insulin production.

• The human body is made up of about 100000 billion cells.
• The largest cell in the human body is the egg cell, or the ovum, which can measure up to 0.035 mm in diameter
• Cells lining the mouth usually last less than three days only, so must be replaced at this rate
• Humans have around 30 000 genes, yet they make up only 3% of our DNA; the remaining 97%, known as 'junk' DNA, apparently does nothing
• There are no standard genetic differences between people of different races. Indeed, there is often greater variation between individuals of the same race than of different races
• An undamaged tooth can retain stable DNA for thousands of years