A revolution has taken place in the last few decades that explains how DNA makes us look like our parents and how a flawed gene can cause disease. This opens the door to treat lot of diseases.
DNA is the basis for all living matter. It means Deoxyribo-Nucleic Acid. It is the hereditary material in humans and almost all other organisms. This is a long fiber, like a hair. It is made from two threads that stick together with a slight twist. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus. All living things on this earth from tiny worms to elephants up to humans share this. According to some scientists, human DNA is 98 percent identical to that of chimpanzees. An important property of DNA is that it can replicate, or make copies of itself.
The information in DNA is stored as a code made up of four chemical bases. They are A (adenine), C (cytosine), G (guanine) and T (thymine). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order or sequence of these bases decides the information obtainable for building an organism.
In fact, these four base chemicals are constructing our genes. The genes take the orders for making all proteins that are available in a cell. The proteins in a cell choose what jobs that cell will do. As well the genes decide how the different cells will be arranged. In this fashion, DNA controls how many fingers we have, where our legs are placed on our body and even the color of your eyes. DNA is a particular bio-molecule. The entire DNA in a cell is found in individual pieces, called chromosomes.
A chromosome is made up of DNA and the proteins attached to it. There are 23 pairs of chromosomes in a human cell. One of each pair was inherited from our mother and the other from our father. Believe it or not, we share the same number of genes as the common mustard weed. If the entire DNA in the human body were put end to end, it would reach the sun and back 600 times. It is interesting to note that we all share about 99 percent of the same DNA as our neighbour and even more with our parents and children. Difference may sound very little but it stands for three million dissimilarities in the three billion long DNA chain. Interestingly DNA detection can be fairly effective if used intelligently. Portions of the DNA sequence that vary the most among humans must be used; also, portions must be large enough to overcome the fact that human mating is not absolutely random.
Forensic-DNA typing, a revolutionary concept was first used in 1986 in England in the case of Colin Pitchfork, who was eventually convicted of the sexual assault and murder of two teenage girls. Then again, people who had wrongly confessed to the murders were saved by this technology as well.
In 1985, a year after the development of DNA fingerprinting, the polymerase chain reaction (PCR) was revealed. This revolutionised the field of molecular biology though the technique would not come into practice in forensic cases until the early 1990s. With the DNA-typing technique it is possible to prove the real criminal or murderer. This is also helpful in the identification of missing persons and human remains.
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Dr Rubaiul Murshed
Source: The Daily Star, November 08, 2008