Term
| True or false? Eukaryotes have no opersons, repressors on operators or regulatory proteins. |
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Definition
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Term
| In eukaryotes, the transcription initiation complex binds poorly to the promoter by itself. How is this problem solved? |
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Definition
| Other transcription factors help the transcription initation complex bind to control elements (groups are called enhancers), with the help of DNA-bending proteins and mediator proteins, upstream or downstream from the promotor. |
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Term
| What are the two types of control elements? |
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Definition
1. Proximal - Close to or part of the promoter
2. Distal - Seperated or distant from the promoter |
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Term
| What are the roles of activators and repressors in regulating gene expression? How do activators enhance gene expression in certain cells? How do repressors inhibit gene expression? |
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Definition
| Activators and repressors bind to control elements to encourage or inhibit gene transcription. Different activators for cell specific proteins are only present in applicable cells. Repressors can inhibit gene expression by blocking activators from binding and by binding to the control elements themselves. |
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Term
| What is combinatorial control of gene activation? |
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Definition
| This is when there are several control elements regulating each gene. |
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Term
| How are coordinately-controlled genes related? |
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Definition
| They are similar to operons in bacteria. Each gene has copies of the same control element (ex. SRE in cholesterol synthesis) which require the same activators (ex. SREBP in cholesterol synthesis). Each gene may code for a protein that works together with the other genes' proteins to accomplish one biosynthetic pathway. These genes may even be on separate chromosomes. |
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Term
| What purpose to histones serve? What are nucleosomes? How are acetylases and deacetylases related? |
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Definition
Histones are positively charged proteins that DNA winds around to form nucleosomes. These can pack together to form the chromosome shape we see during mitosis.
Acetylases acetylates histone tails in nucleosomes to get them to spread apart, while deacetylases does the reverse. |
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Term
| What is the difference between heterochromatin and euchromatin? |
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Definition
Heterochromatin is a tightly folded part of the genome (found in centromers and telomeres) which can't be transcribed, there is no room for the initiation complex.
Euchromatin is the less folded genome. |
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