Transcription elongation in prokaryotes | prokaryotic transcription lecture 3

Summary

This video explores the DNA transcription process in prokaryotic cells, focusing on the elongation phase. It describes how RNA polymerase, along with a sigma factor, initiates transcription by unwinding the DNA to expose the template strand. As ribonucleotides are added to the growing RNA strand in a 5' to 3' direction, a bridge protein ensures accurate nucleotide incorporation. The video also discusses the energy dynamics of transcription and the proofreading capabilities of RNA polymerase, highlighting the importance of fidelity in synthesizing mRNA for protein production.

Takeaways

• 😀 The DNA transcription process in prokaryotic cells begins with initiation, which is crucial for the transcription to occur.
• 😀 RNA polymerase and sigma factor form a holoenzyme that binds to the DNA's start site to initiate transcription.
• 😀 The elongation phase involves adding ribonucleotides to create a long chain of messenger RNA (mRNA).
• 😀 Ribonucleotides are added in a 5' to 3' direction, with the RNA strand complementary to the DNA template.
• 😀 A replication bubble forms during transcription, allowing the DNA strands to separate for RNA synthesis.
• 😀 The bridge protein plays a key role in ensuring proper nucleotide addition during the elongation process.
• 😀 RNA polymerase performs nucleotide pairing and bond formation to ensure the accuracy of the RNA sequence.
• 😀 The proofreading activity of RNA polymerase is less efficient than that of DNA polymerase, potentially leading to errors.
• 😀 Mismatched nucleotides during transcription can result in faulty protein production or cell malfunction.
• 😀 The transcription process includes both energy consumption from nucleotide hydrolysis and proper alignment of nucleotides.

Q & A

What is the first step in the DNA transcription process in prokaryotic cells?

The first step is initiation, where RNA polymerase binds to the DNA at the start site with the help of a sigma factor.

What role does the sigma factor play in the transcription process?

The sigma factor assists RNA polymerase in recognizing and binding to the correct start site on the DNA for transcription.

What happens during the elongation phase of transcription?

During elongation, RNA polymerase synthesizes RNA by adding ribonucleotides complementary to the template DNA strand, moving in the 5' to 3' direction.

What is the significance of the replication bubble in transcription?

The replication bubble forms when DNA strands separate, allowing the template strand to be accessed for RNA synthesis.

How does RNA polymerase ensure the correct nucleotide is added during elongation?

RNA polymerase uses a bridge protein to facilitate the proper binding of each nucleotide, ensuring that only one nucleotide is available for incorporation at a time.

What is the function of the bridge protein in the elongation phase?

The bridge protein helps maintain the accuracy of nucleotide addition by allowing only one template nucleotide to be free for pairing with the incoming ribonucleotide.

What is the direction of RNA synthesis during transcription?

RNA synthesis occurs in the 5' to 3' direction, which means nucleotides are added to the growing RNA strand from the 5' end to the 3' end.

Does RNA polymerase have proofreading capabilities?

Yes, RNA polymerase has a proofreading ability to detect and correct mismatched nucleotides, although it is not as efficient as the proofreading function of DNA polymerase.

What happens if RNA polymerase adds a mismatched nucleotide during transcription?

If a mismatched nucleotide is added, RNA polymerase can shift back and remove the incorrect nucleotide, allowing for correction during RNA synthesis.

What will the end product of the transcription process be?

The end product of transcription is a messenger RNA (mRNA) molecule, which carries the genetic information from DNA to be translated into proteins.