Midterm1 Answers

The histone octamer is made up of two molecules each

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bound where the DNA enters and exits. The histone octamer is made up of two molecules each of H2A, H2B, H3 and H4. 160 bp of DNA wrap around the histone core and the linker between histones is 40bp . 8
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Name________________________________ PART TWO OF TWO PART TWO OF TWO PART TWO OF TWO Biology E-14 Midterm I Harvard University February 15, 2010 OPEN BOOK/NOTES TAKE-HOME EXAM. ANSWER ALL QUESTIONS IN THE SPACE PROVIDED . DUE MARCH 1 st 5:30pm. PLEASE WRITE YOUR NAME AT THE TOP AND INITIAL EACH PAGE. SHOW ALL WORK FOR FULL OR PARTIAL CREDIT. CALCULATORS PERMITTED. WORK INDEPENDENTLY, DISCUSSION WITH OTHER PEOPLE IS NOT PERMITTED. Undergraduate and Graduate Credit Exam: 100%=100 points, 14 QUESTIONS, 12 PAGES (2 parts) 13 . Lactose intolerance is caused by an inability to digest and absorb lactose due to insufficient production of the enzyme lactase. Consequently, bacteria in the colon take up the undigested lactose; this leads to production of toxic byproducts, which evoke intestinal reactions. Because you are a geneticist, you are aiming at finding a treatment for patients with lactose intolerance using genetic tools. Assume that you know the sequence for the human lactase gene. a) You are trying to determine whether there are mutations in the lactase gene which could be responsible for the insufficient lactase production in your patients. Name and briefly describe two possible methods to identify potential mutations. (4 points) Restriction Fragment Length Polymorphism (RFLP): mutations in the gene could have altered recognition sites of restriction enzymes in the gene sequence; clone or PCR out gene from healthy person and patient; digest with restriction enzymes, gel electrophoresis (Southern Blot), and compare healthy vs lactose- intolerant pattern. A change in the pattern is indicative of a mutation in the sequence. PCR and Sequencing: use polymerase chain reaction to amplify gene from patient, sequence and compare to known reference sequence of healthy person. And others… b) Briefly describe two potential treatments (can be futuristic) for the patients that involve the use of genetic tools. One of your treatments should result in a temporary solution and the other, a permanent solution. (4 points) temporary : Produce recombinantly expressed lactase (for example in yeast). Clone human lactase gene into expression vector, introduce into host cell and induce production; harvest and supply as pills (has to be taken with every consumption of dairy products). permanently (futuristic): gene therapy; extract intestinal stem cells from patient. Replace mutated version of lactase gene with functional version using a genetically altered (lenti-)virus. Re-introduce transgenic stem cells into patient. Long-term restoration of lactase production.
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The histone octamer is made up of two molecules each of H2A...

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