Sunday, 25 November 2012

The Story of DNA

What is DNA? DNA is an abbreviation of DeoxyriboNucleic Acid. It is a hereditary material located in the nucleus of a cell of living organisms (including humans). It is also considered as building blocks of living organisms. The DNA consists of four basic units (called as bases) - adenine, thymine, cytosine and guanine. The structure of DNA is in double helix. The double helix structure of DNA was discovered by Crick and Watson in 1953 - one of the great discoveries of the century - and both of them (including Wilkins) received Nobel Prize in 1962.

The left stamp depicts the 1962 Nobel Prize recipients for the discovery of the double helix of DNA. The solving of double helix structure was partly based on the X-ray diffraction image on DNA (shown on the left stamp). The right stamp depicts the 1978 Nobel Prize recipients for breaking the DNA codes.

In DNA structure, base adenine (A) is always paired with base thymine (T) and base cytosine (C) is always paired with base guanine (G). This stamp sheetlet has a perfect composition to show the base pairing of DNA.

this miniature sheet also shows a nice composition of base pairing of DNA

this miniature sheet depicts the model of double helix DNA structure

Below are a few stamps which have image of double helix DNA structure.

The double helix DNA attributes to chromosomes (in other words, chromosomes consist of DNA), and this information is well presented by the stamp below.

The methods of DNA sequencing (to read the order of bases in the double helix DNA structure or to read genetic codes of the DNA/gene) were developed in 1970s. Two methods were developed - Maxam Gilbert method and Sanger method. However, only Sanger method is adopted as a common approach for DNA sequencing. In fact, the DNA sequencing of human genome (completed in 2003) was done using Sanger method. The stamps below depict the Sanger DNA sequencing.

The chromatogram of DNA sequences is shown at the top right corner of the stamp

The two stamps depict the double helix DNA structure and the location of DNA in the chromosomes. However, the interesting part of these stamps is the stamp gutter showing the chromatogram of DNA sequences.