At some point in our period of learning as life scientists, we must seek to understand how genetic information travels around the biological system. Simply put, understanding of how traits are passed from one biological system to another is a major key in life sciences. Without it, studying life will not make any sense. In this post and the next few to come, we will try to elucidate the mechanisms of information transfer within living organisms.

An illustration of the central dogma theory : credit

As a biochemist, I first came across the central dogma theory during my 200 level in the university. It formed the basis of introductory genetics and biochemistry. The theory serves as an explanation of how genetic information flow within living organisms.

Occupying the center of the Central Dogma Theory (CDT) is the Deoxy Ribonucleic Acid (DNA). The DNA has been proven to be responsible for storing genetic information in living organisms as demonstrated by Griffith's transformation experiment. It is usually found in the nucleus and some organelles like the mitochondrion and chloroplasts of cells. The DNA has a unique ability of making copies of itself in a process known as replication. The genetic information on the DNA can also be transcribed into Ribonucleic Acid (RNA) in a process known as transcription before being finally translated into proteins to complete the CDT. This means genetic information are locked in the protein which is made up of many several amino acids. The various processes in the CDT are irreversible.

Nature and structure of Deoxy ribonucleic acid

All living organisms store genetic information in form of DNA except some ribonucleic acid viruses. Generally, DNA in all living organisms have more or less the same chemical backbones which are;

1. Phosphate group
2. Deoxyribose sugar
3. Nitrogenous purine or pyrimidine base

DNA components I credit

The purine bases are of two types - adenine and guanine, while the pyrimidine are also of two types - thymine and cytosine. These chemical backbones are arranged in nucleotide chains with each chain being made up of one deoxy ribose sugar, a phosphate group and a purine or pyrimidine base. Basically, the DNA of all organisms are similar both in structure and components. There were several issues concerning the actual structure of the molecules until 1953 when J.D. Watson and F. C. Crick proposed an acceptable structure with some essential features.

Watson and Crick in 1953 Icredit

One of the foremost features of Watson and Crick's structure of the DNA is that it is a double stranded molecule with each strand linked together by weak hydrogen bond. Therefore, little energy is needed to separate these two strands when required. Also, the distance between the two strands are constant throughout the length of the two strands due to specificity of base pairings. For this specificity, the adenine of the purine base always pair with thymine of the pyrimidine base while guanine also pairs with cytosine respectively. Consequently, the knowledge of the base sequence of one of the strands of the molecule is enough to determine the base sequence of the other. Lastly, the two strands are not always in a straight line, they always twist around each other to form a helix, ladder-like structure.

To be continued..........

References

jvi.asm
Biology Arizona
Dictionary.com
NCBI
Data allenai
ua-magazine
khan academy
Explorable
nature
Science direct
History.com