Transcription, Post-transcriptional Processing, Splicing Flashcards
What is the antisense strand?
The antisense strand is the template strand that mRNA is produced from and is complementary to.
What is the sense strand?
The sense strand is the coding strand of DNA that is identical to the new mRNA transcribed, except T nucleotides are U nucleotides.
What is the initiation of transcription?
DNA unwound by helicase and super coil strain reduced by topoisomerase. RNA polymerase II locastes the promoter region (TATA box). Transcription factors help w/ locating and binding. No RNA primer is required to initiate transcription.
How many different types of RNA polymerases are there in eukaryotes and what are their functions?
In what direction is mRNA synthesized/elongated?
mRNA is transcriped/elongated in the 5’ to 3’ direction. The antisense strand is read from the 3’ to 5’ direction by RNA polymerase.
What is heterogenous RNA (hnRNA)?
Heterogenous mRNA is the pre-mRNA that has not undergone splicing.
What is the first posttranscriptional modification?
The first posttranscriptional modification is the adition of a 5’ cap (7-methylguanylate triphosphate) which occurs while the mRNA is still being elongated. The 5’ cap helps protect against degradation and is recognized by ribosome as the binding site.
What is the second posttranscriptional modification?
What is the third posttranscriptional modification?
The third posttranscriptional modification is the splicing of introns from hnRNA (pre-mRNA) and exons ligased together to form mature mRNA which then exits the nucleus.
- Splicing is done by the spliceosome which consists of small nuclear RNA (snRNA) and small nuclear ribonucleoproteins (snRNPs).
- Recognize the 5’ and 3’ end of introns, spliced/excised out and bent into a lariat shape to be degraded in the nucleus.
Where does transcription and posttranscriptional modifications occur?
