INTRODUCTION

The central dogma of molecular biology. Coined by Francis Crick. And in his own words,

"I called this idea the central dogma, for two reasons, I suspect. I had already used the obvious word hypothesis in the sequence hypothesis, and in addition I wanted to suggest that this new assumption was more central and more powerful."

WHAT DOES IT MEAN

The central dogma of molecular biology is a theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly to protein.

HOW DOES IT OCCURE

This process occurs in 3 steps, they are as follows:

1. From existing DNA to make new DNA -DNA replication
2. From DNA to make new RNA -transcription
3. From RNA to make new proteins -translation

1. DNA REPLICATION

DNA must be duplicated in a process called replication before a cell divides. The replication of DNA allows each daughter cell to contain a full complement of chromosomes.

2. TRANSCRIPTION

Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). DNA safely and stably stores genetic material in the nuclei of cells as a reference, or template. Meanwhile, mRNA is comparable to a copy from a reference book because it carries the same information as DNA but is not used for long-term storage and can freely exit the nucleus. Although the mRNA contains the same information, it is not an identical copy of the DNA segment, because its sequence is complementary to the DNA template.

Transcription is carried out by an enzyme called RNA polymerase and a number of accessory proteins called transcription factors. Transcription factors can bind to specific DNA sequences called enhancer and promoter sequences in order to recruit RNA polymerase to an appropriate transcription site. Together, the transcription factors and RNA polymerase form a complex called the transcription initiation complex. This complex initiates transcription, and the RNA polymerase begins mRNA synthesis by matching complementary bases to the original DNA strand. The mRNA molecule is elongated and, once the strand is completely synthesized, transcription is terminated. The newly formed mRNA copies of the gene then serve as blueprints for protein synthesis during the process of translation.

3.TRANSLATION

In Molecular Biology, the term translation can be defined as the process of converting nucleic acid information into amino acids. It also relates to the process of producing proteins from mRNA templates.

During the process of translation, sequence of nucleotide present on the RNA is translated into amino acid sequence of proteins. The complete reaction of translation is carried out by ribosomes, where both ribosomes and tRNA dock on a matured mRNA transcript and select multiple enzymes in an energy-intensive process that uses ATP as well as GTP.

Components of Translation

The main components of translation include ## :

• mRNA of both Eukaryotes and Prokaryotes
• tRNA – It helps in sending commands or transferring the information between protein and nucleic acids.
• Ribosomes – It contains ribosomal RNA and proteins, therefore, it is called the manufacturing unit of a cell.
• Enzymes: It is required for the formation of a peptide bond between the amino acids and also to attach amino acids to the accurate tRNA molecules.
• Proteins- They are the soluble factors, which are required for proper initiation, elongation and termination of translation.

Process Translation

Translation proceeds in three different stages or phases and every stage is associated with different proteins. Both GTP and ATP are the main source of energy used in this process. The three different stages of translation mechanism are:

• Activation or charging of tRNA
• Initiation – recognition of start codon, binding of ribosomal subunits to mRNA and formation of initiation complex with Met-tRNA at the P site
• Elongation – peptide bond formation and growing of polypeptide chain
• Termination – stop codon enters the A site, resulting in the termination of the process.