6.Prokaryotic gene transcription, its steps, enzymes involved in its mechanism

Answer 1

Prokaryotic gene transcription is the process by which the genetic information encoded in DNA is transcribed into RNA molecules. This process occurs in the cytoplasm of prokaryotic cells and is essential for protein synthesis.

The steps involved in prokaryotic gene transcription are as follows:

1. Initiation: The first step in gene transcription is initiation. The RNA polymerase enzyme binds to a specific DNA sequence called the promoter region, which is located upstream of the gene to be transcribed. The RNA polymerase unwinds and separates the DNA strands, creating a transcription bubble.

2. Elongation: Once the RNA polymerase has bound to the promoter region, it moves along the DNA template strand in the 3' to 5' direction, synthesizing an RNA molecule in the 5' to 3' direction. As it moves, the RNA polymerase adds complementary RNA nucleotides that are base-paired with the exposed DNA template strand.

3. Termination: The final step in gene transcription is termination. In prokaryotes, there are two types of termination: Rho-dependent and Rho-independent termination. In Rho-dependent termination, a protein called Rho binds to the newly synthesized RNA molecule, causing the RNA polymerase to dissociate from the DNA template strand. In Rho-independent termination, specific DNA sequences on the RNA molecule form a hairpin loop followed by a string of uracil bases, which destabilizes the RNA-DNA hybrid and leads to RNA polymerase dissociation.

The enzymes involved in the mechanism of prokaryotic gene transcription include:

1. RNA polymerase: This enzyme is responsible for synthesizing RNA molecules from a DNA template. It binds to the promoter region and catalyzes the addition of RNA nucleotides to the growing RNA chain.

2. Sigma factor: In prokaryotes, RNA polymerase is associated with a sigma factor, which helps the enzyme recognize and bind to the promoter region on the DNA template strand.

3. Rho protein: This protein is involved in Rho-dependent termination. It binds to the newly synthesized RNA molecule and causes the RNA polymerase to dissociate from the DNA template.

Overall, prokaryotic gene transcription is a complex process that involves the interaction of various enzymes, such as RNA polymerase, sigma factor, and rho protein, to ensure accurate and efficient synthesis of RNA molecules from DNA templates.