Question

Describe the process of transcription in protein synthesis.

Answer 1

The process of copying of genetic information from one (template) strand of DNA into a single-stranded RNA transcript is called transcription.

The process of transcription is as follows:

1. For transcription, promoter, structural gene, and terminator (together called transcription unit) are required.
2. The DNA strand used for the synthesis of RNA is called antisense or template strand which is oriented in 3' → 5' direction, while the other strand not involved in RNA synthesis is called the coding strand. It is oriented in 5' → 3' direction.
3. A small DNA sequence which provides a binding site for RNA polymerase is called promoter which is present towards 5' end/upstream, while a small DNA sequence which terminates the transcription process called terminator is present towards 3' end/downstream.
4. The process of transcription, in both prokaryotes and eukaryotes, involves three stages viz. Initiation, Elongation, and Termination.
5. During initiation, RNA polymerase binds to the promoter and moves along the DNA and causes local unwinding of DNA duplex into two chains in the region of the gene.
6. Exposed ATCG bases project into the nucleoplasm.
7. Only one strand functions as template (antisense strand) and the other strand is complementary which is actually a coding strand (sense strand).
8. During elongation, the ribonucleoside triphosphates join bases of the DNA template chain.
9. As transcription proceeds, the hybrid DNA-RNA molecule dissociates and makes mRNA molecules free.