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rna processing and c
micro RNA
| Question | Answer |
|---|---|
| What do hormone receptors do? | Activate transcription by binding to specific genes and recruiting co-activators |
| When the cell recognizes DS RNA, _________ cleaves it into __________ | dicer, siRNA |
| When siRNA interfere with ______, it can perform these four things. | RITS, 1. transcript silence 2. histone methylation 3. DNA methylation 4. transcriptional repression |
| Explain the 2 step process of splicing of pre-mRNA. Draw a lariet structure | 1. An adenine in intron sequence attacks the 5' splice site, leaving an open -OH 2. The 3' -OH leaft over on exon 1 attacks the phosphate on exon 2, and releases lariet |
| What is a spliceosome? And what is an SnRNP? | A catalyst and protein complex. A SnRNP is a small ribonuclear protein, which recognizes splicing sequences |
| Explain and identify the 4 SnRNPs and their functions | U1: 51 splice site U2: branch point at Adenosine sis signaled by BB and U2AF U4/U6: splits 5' site and binds to 2'-OH U6: joins exons and removes lariet U5: helps U4 and U6 |
| What happens, chemically, during splicing? | Base pairs are rearranged and formed between SnRNPS |
| What are 2 ways to control RNA-splicing mechanisms? | exon definition model and alternative splicing |
| Explain the exon definition model in short | defines positions of U1 and U2, and whatever is placed in-between them is an intron |
| Explain alternative splicing | A sequence can have multiple exons, but the cell may only decide to keep one from each "group". |
| Which control (splicing) requires an activator, and which requires a repressor? | Negative - repressor to stop Positive - activator to start |
| What are the differences between group 1 and group 2 self splicing introns? | Both sites break on group 1 and there is no re-attachment of a lariat, it also includes a Guanosine branch point. Group 2 involves branch point at A and formation of a lariat |
| Where are RNA modifying proteins found? | On activated amino acids |
| How do amino acids become activated? | Phosphorylation at a serine residue |
| Name three things that RNA modifying proteins can do | 1. cap 5' end of RNA 2. cleave 3' end of RNA 3. aid in processing 3' end of RNA |
| What are three important things to remember about formation of 3' ends of mRNA? | 1. GU rich sequences are cleaved 2. -CA- is the point of cleavage 3. the poly A site is added to the end that was cleaved |
| Of the three places to remember for formation of 3' ends of mRNA, what proteins are associated with them? | poly A - CSTF -CA- cleavage factor GU-rich sequence - CPSF protein |
| What will a long DNA transcript form, and what will a short DNA transcript form? | Long - membrane bound antibody with terminal hydrophobic peptide Short - secreted antibody with terminal hydrophilic peptide |
| Explain RNA editing, U-bases | RNA transcripts can have sites with missing U nucleotides. Guide RNA1 specifies sites with missing U nucleotides. Guide mRNA2 pairing allows editing. |
| Explain RNA editing in mammals | ADAR enzymes scan the RNA transcript and deaminates A hairpins and creates inosine |
| Where does RNA editing occur? | mitochondria |
| What happens to mRNA during their export to the cytoplasm? | they exchange proteins. |
| What are 4 translational controls, in short? | 1. proteins block access to sequence 2. temperatures deform Rstem loop 3. small molecules alter shape of shine dalgarno sequence 4. antisense RNA hybridizes to S-D sequence |
| In what state does protein synthesis slow down (regarding g-proteins) | If eIF2B is in an inactive complex with phosphorylated eiF2 and GDP |
| What does eiF2B do? | Acts as a facilitator for activating eIF2 with GTP. it is recycled |
| How can mRNA be degraded? | From either end of RNA |
| What assists in mRNA degradation? | deadenylase shortens poly-a tail, then exposes 5' to enzymes |
| What happens in low iron levels? | Aconitase represses translation of ferritin. Transferrin receptor is made |
| What happens in high iron levels? | The aconitase becomes activator for ferritin after Fe binds to it and it is removed. When removed, no transferrin receptor is made. |
| How is rRNa formed? | Transcribed from DNA using RNA polymerase I. |
| What does rRNa start out as | Precursor rRNA, which is cleaved into respective sequences for subunits (e.g. 18S, 28S, 30S, 60S) |
Created by:
neeck
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