Term
| What is a transcription unit? |
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Definition
| A sequence of DNA under control of one promoter |
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Term
| How many genes are usually in a transcription unit? |
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Definition
| Usually just one in humans |
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Term
| Things that are upstream of the start of transcription are noted as negative or positive? |
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Definition
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Term
| What happens to the RNA transcript? What do these modifications do? |
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Definition
| Introns spliced out. 7-Methyl G cap on 5' end. Poly-A tail on 3' end. These things protect the RNA from degradation. |
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Term
| What is an intron and what is a exon? |
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Definition
| Exons are expressed sequences. Introns are not expressed. They are intervening sequences and stay in the nucleus. |
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Term
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Definition
| The untranslated region is the part of DNA included in the mRNA, but not part of the protein. These sequences occur before the start codon and after the stop codon. (There is a 5' and a 3' UTR) |
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Term
| Are there different RNA polymerases, or only one? |
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Definition
| there are a few different ones in humans. Pol I is for rRNA. Pol II is for mRNA (but less than 5% of total RNA) and Pol III is for tRNA. |
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Term
| What is a really famous core promoter element? (Hint: it is a box) Where is it found? |
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Definition
| the TATA box. It is found about 25 to 30bp upstream of start site. |
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Term
| Where is the initiator region? Is it the same as the TATA box? |
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Definition
| It is different from the TATA box. It is around the start site. |
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Term
| What are the things that bind DNA and get transcription started? |
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Definition
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Term
| Which TF binds the TATA box? |
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Definition
| TFIID has TATA binding protein (TBP) and about 10 TAFs (TBP-associated factors) |
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Term
| What are the 4 main steps of transcription? |
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Definition
| Pre-initiation complex formation, initiation, elongation, termination |
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Term
| What happens during pre-initiation complex formation? |
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Definition
| TFIID binds with the TBP part on the TATA box. Then RNA poly II comes in and binds to the complex. Then, TFIIH phosphorylates RNA Pol II and releases it so that it can proceed down the DNA template. |
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Term
| What does DNA look like in the area of transcription? What does this? |
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Definition
| It looks like a bubble because TFIIH helicase opens it up. It gradually unwinds as it goes. |
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Term
| What is it called when RNA poly II is released from the initiation complex? |
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Definition
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Term
| How many phosphate groups do the nucleotides have as transcription proceeds? |
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Definition
| They all come in with three phosphates. The first one in the chain keeps its 3 phosphates. The second and onwards lose two, and this powers RNA Pol II. |
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Term
| When is the 5' cap added? What is the 5' cap called? What does this do? |
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Definition
| 7-Methyl-G cap is added after the first several nucleotides are incorporated. |
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Term
| How fast is transcription? |
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Definition
| appx 50 nucleotides per second (so it takes like 10 hours for a large gene) |
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Term
| What helps relieve tension in the DNA molecule as it is pulled on by transcription? |
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Definition
| DNA topoisomerase snips a strand of DNA to allow it to be not so tense. Then it reanneals it. |
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