Podcast
Questions and Answers
What is the first step in the initiation of transcription?
What is the first step in the initiation of transcription?
What occurs during the elongation phase of transcription?
What occurs during the elongation phase of transcription?
Which type of RNA polymerase produces mRNA?
Which type of RNA polymerase produces mRNA?
What is the role of spliceosomes in the splicing process?
What is the role of spliceosomes in the splicing process?
Signup and view all the answers
In alternative splicing, what is the significance of the different spliced mRNA products?
In alternative splicing, what is the significance of the different spliced mRNA products?
Signup and view all the answers
What terminates the transcription process in RNA polymerase II?
What terminates the transcription process in RNA polymerase II?
Signup and view all the answers
What is the function of enhancers in the context of gene expression?
What is the function of enhancers in the context of gene expression?
Signup and view all the answers
Which of the following correctly describes a core promoter?
Which of the following correctly describes a core promoter?
Signup and view all the answers
Study Notes
Transcription
-
Initiation: Transcription factors (TFs) bind to the promoter region, allowing RNA polymerase to attach. TFs, RNA polymerase II, and mediator proteins form the basal apparatus.
-
Elongation: DNA moves through the RNA polymerase channel, making a sharp turn at the active site. DNA strands separate, and new RNA nucleotides are added to the template strand. The DNA-RNA hybrid encounters structural obstacles, and the strands separate to form a new mRNA strand.
-
Termination: No specific termination sequence for RNA polymerase II. RNA polymerase continues until an exoribonuclease reaches the enzyme.
Splicing
-
Splicing components: Pre-mRNA contains a 5' splice site (GU at the beginning of the intron) and a 3' splice site (AG at the end). Spliceosomes (containing snRNA and about 300 proteins) mediate splicing.
-
Process:
-
5' splice site is cut and attached to the branch point adenine (lariat forms).
-
3' splice site is cut, and the two exon extremities are covalently linked. (lariat intron degrades).
-
Alternative splicing: The same mRNA molecule can be spliced in different ways, generating different mRNA products and proteins.
RNA Polymerase Types
- Different types of RNA polymerase exist, each with a specific cellular location and related transcription products. Examples include: RNA polymerase I (nucleolus, 5.8S, 18S, and 28S rRNA); RNA polymerase II (nucleoplasm, mRNA, snRNA); RNA polymerase III (nucleoplasm, tRNA, 5S rRNA); and RNA polymerase (mitochondria, mitochondrial rRNA).
Enhancers and Silencers
- Enhancers and silencers are nucleotide sequences where transcription factors bind. Enhancers increase gene expression, and silencers decrease it.
Promoters
- Promoters are DNA sequences that control RNA polymerase binding. A promoter's core region initiates transcription, often containing a TATA box. Regulatory regions help control the transcription rate.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the essential processes of transcription and splicing in molecular biology. It includes the roles of transcription factors, RNA polymerase, and spliceosomes in the generation of mRNA. Test your understanding of these critical biological mechanisms.
