Question

(2 A4 pages) Describe, with the aid of diagrams, the process of RNA transcription, including the enzyme(s) involved (90%) and give two examples of drugs/toxins that affect the process (10%).

Answer 1

Process of RNA Transcription

Transcription is the process in which DNA molecule is transcripted into RNA by the enzyme RNA polymerase. Transcription process takes place in the nucleus of the cell. DNA is used as a template for synthesis of the RNA molecule and later RNA leaves the nucleus and goes to the ribosome located in the cytoplasm for the process of translation.

Diagram for process of transcription

Initiation RNA polym RNA polymerase DXIMULTA promoter region Hongation TTTTTTTY stop sequence RNA polymerase Termination RNA Sequence

Steps of transcription

1. Initiation.

RNA polymerase binds to a sequence of DNA called the promoter region and separates the DNA strands and provide a template for transcription.

2. Elongation.

DNA strand act as the template strand for RNA polymerase. The RNA transcript contains the same information as a complementary strand of DNA, but the thymine (T) is replaced by uracil (U).

3. Termination

Terminator is a sequence that signal for termination of RNA transcription. The RNA Polymerase releases at the end of the transcription.

Example of drug/ toxin that inhibit transcription - α-Amanitin and actinomycin D

α-Amanitin is the toxin from mushroom species and actinomycin D is the commonly found antibiotic/ drug that inhibits transcription process.