Transcription Basics

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Questions and Answers

What is the function of RNA polymerase in transcription? How does it differ in prokaryotes and eukaryotes?

RNA polymerase is responsible for synthesizing RNA from a DNA template during transcription. In prokaryotes, a single RNA polymerase performs this function, while eukaryotes have multiple RNA polymerases (I, II, and III) each responsible for transcribing different types of RNA.

Describe the key steps of transcription in eukaryotic cells.

The key steps include: initiation (RNA polymerase and transcription factors bind to the promoter), elongation (RNA polymerase synthesizes RNA), and termination (RNA synthesis stops and RNA is released).

What is the role of the promoter region in transcription initiation?

The promoter region is a DNA sequence where RNA polymerase and associated transcription factors bind to initiate transcription.

How do transcription factors regulate gene expression in eukaryotes?

Transcription factors bind to specific DNA sequences near genes and can either enhance or repress transcription by influencing RNA polymerase activity. Signup and view all the answers

Why is the TATA box important in transcription?

The TATA box is a DNA sequence in the promoter region that helps to position RNA polymerase for proper transcription initiation. Signup and view all the answers

Compare the functions of RNA polymerase I, II, and III in eukaryotic transcription.

RNA polymerase I transcribes ribosomal RNA (rRNA), RNA polymerase II transcribes messenger RNA (mRNA) and some small nuclear RNAs (snRNAs), and RNA polymerase III transcribes transfer RNA (tRNA) and other small RNAs. Signup and view all the answers

How does RNA polymerase recognize where to start and stop transcription?

RNA polymerase recognizes the start site through the promoter region and transcription factors. Termination occurs at specific termination sequences or through other termination signals. Signup and view all the answers

Explain the role of enhancers and silencers in transcription regulation.

Enhancers increase transcription levels by binding activator proteins, while silencers decrease transcription levels by binding repressor proteins. Signup and view all the answers

What happens if there is a mutation in the promoter region of a gene?

A mutation in the promoter region can alter the binding of RNA polymerase and transcription factors, leading to changes in gene expression (either increased or decreased). Signup and view all the answers

How does rho-dependent termination differ from rho-independent termination in prokaryotes?

Rho-dependent termination involves the Rho protein binding to the mRNA and moving towards RNA polymerase, causing it to dissociate. Rho-independent termination relies on a hairpin loop structure in the RNA followed by a series of uracil bases, causing the RNA polymerase to stall and release. Signup and view all the answers

What are the three major post-transcriptional modifications of eukaryotic mRNA?

The three major post-transcriptional modifications are: 5' capping, 3' polyadenylation (addition of a poly(A) tail), and RNA splicing. Signup and view all the answers

Why is the 5' cap added to mRNA, and what role does it play in translation?

The 5' cap protects the mRNA from degradation and enhances translation by facilitating ribosome binding. Signup and view all the answers

Explain the function of the poly(A) tail. How does its length affect mRNA stability?

The poly(A) tail protects the mRNA from degradation and enhances translation. Longer poly(A) tails generally increase mRNA stability and translational efficiency. Signup and view all the answers

What is alternative splicing, and how does it contribute to protein diversity?

Alternative splicing is a process where different combinations of exons from the same gene are joined together, resulting in multiple mRNA isoforms. This leads to the production of different proteins from a single gene, increasing protein diversity. Signup and view all the answers

How does improper splicing lead to genetic disorders? Provide an example.

Improper splicing can result in the inclusion of introns or the exclusion of exons, leading to non-functional or misfolded proteins. For example, mutations affecting splicing of the SMN1 gene can cause spinal muscular atrophy. Signup and view all the answers

Which strand is important for transcription and why?

Template Strand (Antisense Strand) The RNA polymerase reads this strand in the 3′ to 5′ direction to synthesize RNA in the 5′ to 3′ direction. Signup and view all the answers

Flashcards

RNA Polymerase Function

RNA polymerase synthesizes RNA from a DNA template during transcription. In prokaryotes, a single RNA polymerase performs this function, while eukaryotes have multiple specialized RNA polymerases.

Eukaryotic Transcription Steps

Transcription in eukaryotes involves initiation, elongation, and termination. Initiation requires transcription factors and promoter binding. Elongation synthesizes RNA. Termination releases RNA polymerase.

Promoter Region Role

The promoter region initiates transcription by serving as the binding site for RNA polymerase and transcription factors.

Transcription Factors

Transcription factors regulate gene expression by enhancing or repressing the rate of transcription.