Final Bio 202 DB Clarification Post 8 Lec 34-39 Su19 kms.pdf - Bio 202 Summer 2019 DB Clarification Lectures 34-39 Lecture 34 Regulation of Eukaryotic

Final Bio 202 DB Clarification Post 8 Lec 34-39 Su19...

This preview shows page 1 - 3 out of 6 pages.

Copyright 2019 Biology Online Bio 202 Summer 2019 DB Clarification Lectures 34-39 Lecture 34: Regulation of Eukaryotic Gene Expression 1. Cholesterol Synthesis What is true about cholesterol synthesis in human cells? A. Genes for enzymes that make cholesterol are in an operon B. Genes for enzymes that make cholesterol are all expressed from 1 promoter *C. Genes for enzymes that make cholesterol are all regulated by SRE-BP D. SRE-BP is an enzyme that catalyzes one step in cholesterol synthesis Response: This question tests your understanding of a specific example of eukaryotic transcription using the cholesterol biosynthetic pathway. Some cholesterol is necessary for the health of human cells. If there is no cholesterol available in the bloodstream from diet, cells will synthesize their own. All genes in the cholesterol biosynthesis pathway are located on different chromosomes but are coordinately controlled so they can all be expressed at the same time for efficient cholesterol production. This falsifies choices A and B. Cholesterol synthesis is controlled by the binding of activators called sterol response elmenent binding proteins (SRE-BP) to control elements called sterol response elements (SRE). Each of the genes that code for enzymes of the cholesterol synthesis pathway has an associated SRE. When cholesterol in the diet is scarce, SRE-BP binds to SREs to stimulate transcription. This supports choice C. The enzymes that catalyze the steps in cholesterol synthesis are translated from the mRNA of the genes that are connected to the SREs. This falsifies choice D and confirms choice C as the best answer. 2. Euchromatin and HeterochromatinWhich of the following is NOT a difference between heterochromatin and euchromatin? A. Euchromatin has areas that can be transcribed, whereas heterochromatin is silent. B. Heterochromatin is tightly packed, whereas euchromatin is less dense. C. Heterochromatin stains darkly, whereas euchromatin stains lightly. *D. Heterochromatin is found in the nucleus, whereas euchromatin is in the cytoplasm. Response: Euchromatin is the active chromatin that undergoes transcription (gene expression) whereas heterochromatin is inactive, silenced. These names are derived from the specific staining of the chromatin with stained heterochromatin appearing darker and stained euchromatin appearing lighter. Functionally, heterochromatin is packed tighter by its proteins preventing access of transcription factors, and euchromatin is less dense, allowing easier access to DNA for transcription. Choices A C can be falsified because they accurately describe major distinguishing proprties of euchromatin and heterochromatin. Heterochromatin and euchromatin are different states of chromatin packing. Regions of heterochromatin and euchromatin can be
Image of page 1

Subscribe to view the full document.