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Biology Chapter 16
Gene Expression part 1 (16.1-16.4)
| Question | Answer |
|---|---|
| What type of cell in the body usually have the same DNA? | Somatic cells. Gametes, red blood cells, and some immune system cells, usually do not have the same DNA as the host. |
| Define gene expression. | The process of turning on a gene to produce RAN and protein. |
| Where, in prok, does the control of gene expression occur? | Usually/mostly at the transcription level. |
| In prok, what is the primary method to control what type of protein and how much is expressed? | DNA transcription. |
| What do ribosomes do? (in euk) | They translate RNA into proteins. |
| How are transcription and translation physically separated? | By the nuclear membrane. Transcription happens inside the nucleus and translation happens outside the nucleus in the cytoplasm. |
| Where can regulation of gene expression happen (in euk)? | It can happen at all stages of the process. |
| What is epigenetic level? (In euk) | When the DNA is uncoiled and loosened from nucleosomes to bind transcription factors. |
| What is transcription level? (In euk) | When RNA is transcribed. |
| What is post-transcription level? (In euk) | When the RNA is processed and exported to the cytoplasm after it is transcribed. |
| What is translational level? | When the RNA is translated to protein. |
| What is post-translational level? | After the protein has been made. |
| Name the main difference between prok and euk gene expression regulation. | Prok gene expression usually happens almost simultaneously while euk gene expression is regulated at many levels. |
| Describe the prokaryotic DNA. | It is supercoiled into a circular chromosome, suspended in the cytoplasm within the nucleoid region of the cell. |
| What is an operon? | It is a collection of genes involved in a pathway that are transcribed together as a single mRNA in prok cells. |
| Name the 3 types of regulatory molecules affecting the expression of operons. | Repressors, activators, and inducers. |
| Which of those 3 are are made in the cell? | Repressors and activators. These proteins regulate gene expression by binding to specific DNA sites adjacent to the genes they control. |
| What, specifically, do repressors and activators bind to? | Repressors bind to operator regions and activators bind to the promoter site. |
| What does a repressor protein do? | It prevents transcription of a gene in response to an external stimulus. |
| What does an activator protein do? | It increases the transcription of a gene in response to an external stimulus. |
| What is an inducer? | A small molecule that may be made by the cell or found in the cell's environment. It either activates/represses transcription depending on the needs of the cell and availability of the substrate. |
| What is tryptophan? | An important amino acid that can be made by prok cells when needed. |
| What is a trp operon? | A series of genes needed to make tryptophan in prok cells. |
| What are the 3 important regions of the trp operon? | The coding region, trp operator, and the trp promotor. |
| What is the operator? | The region of DNA outside of the promotor region that binds activators/repressors that control gene expression in prok cells |
| What is the lac operon? | It encodes the genes needed to acquire and process the lactose from its environment. The Z gene of the lac operon encodes beta-galactosidase (it breaks down glucose/galactose). |
| What are epigenetic changes (euk)? | Changes in gene expression that don'/t result from changes in the DNA sequence. |
| How can transcriptional access to the DNA be controlled? | By chromatin remodeling and DNA methylation. |
| What is chromatin remodeling? | It changes the way that DNA is associated with chromosomal histones. |
| What is DNA methylation? | It is associated with developmental changes and gene silencing. |
| What is the first level of organization for DNA? | Packing. This is where the DNA is wound around histone proteins called nucleosomes. |
| What do nucleosomes do? | They control the access of proteins to the DNA. (they look like beads on a string.) |
| What causes nucleosomes to pack tightly together? | Methylation of DNA and histones. Therefore, transcription factors cannot bind the DNA, and genes are not expressed. |
| What is histone acetylation? | The addition of acetyl groups to the histone "tails" that causes the nucleosomes to loosen, and therefore express their genes. |
| What is DNA methylation? | The addition of methyl groups onto the DNA. This happens in regions called CpG islands (areas with high frequency of cytosine & guanine dinucleotide pairs in promotor regions of genes). |
| What is the effect of DNA methylation? | Silenced (unexpressed) genes. |
| What is a transcription factor? | A protein that binds to the DNA at the promoter or enhancer region and that influences transcription of a gene. |
| What is different about euk RNA pol when compared to prok cells? | Eukaryotic RNA polymerases need other proteins (transcription factors) to facilitate transcription start. |
| What two types of transcription factors regulate euk transcription? | General (basal) transcription factors (bind to core promotor region to assist with binding of RNA pol) and specific transcription factors (binds outside of core promotor region). |
| Where is the promotor region? | Upstream (before) of the coding sequence. |
| What is the function of the promotor? | To bind transcription factors that control the initiation of transcription. |
| What is a cis-acting element? | Transcription factor binding sites within the promotor that regulate the transcription of a gene adjacent to it. These factors bind upstream of the encoded gene. |
| What are enhancers? | A segment of DNA that can be anywhere, even on a different chromosome. It influences the transcription of a specific gene. They are binding sites for specific transcription factors. |
| What do bending proteins do? | They bend a segment of DNA to let the enhancer and the gene segment to come together. |
| What are enhancers made of? | Short DNA sequences called distal control elements. Activators bind to these elements and interact with mediator proteins and transcription factors. |
Created by:
tali_Alley
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