quiz2s05a - MIT Department of Biology 7.013 Introductory...

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7.013 Quiz 2 ANSWERS Question Value Score 1 14 2 16 3 16 4 24 5 17 6 13 100 MIT Department of Biology 7.013: Introductory Biology - Spring 2005 Instructors: Professor Hazel Sive, Professor Tyler Jacks, Dr. Claudette Gardel
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Question 1 a) What role does the acrosome have in fertilization? Circle all that apply. 3 pts i) It responds to egg’s chemoattractants. ii) It has enzymes that digest the zona pellucida. iii) It has enzymes that digest the nuclear membrane. iv) It is the part of the egg that prevents sperm from binding. v) None of the above. b) If calcium is injected into an unfertilized sea urchin egg, what would happen? Circle one. 3 points i) Capacitation would occur. ii) A slow block to polyspermy would be induced. iii) The egg will become fertilized without sperm. iv) The egg will become female. v) The sperm will undergo an acrosomal reaction. c) If we now mix sea urchin sperm with these eggs (in b), will fertilization occur? Circle one. 3 points i) No, capacitation has already occurred. ii) No, the sperm can no longer attach to the egg. iii) Yes, the egg is now in “ready state”. iv) No, the egg is already fertilized. v) None of the above. d) Could a human sperm fertilize a hamster egg? Explain your answer briefly. 5 points No, the egg is protected by a thick zona pellucida that can be penetrated only if the ZP3 ligands within can be bound by the sperm with the appropriate receptor. These interactions are species specific. This triggers the acrosomal reaction which spills out hydrolytic enzymes to make a passage of the sperm through the Zona Pellucida. 2
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I 3 Name______________________________ Question 2 You wish to make your pet glow in the dark so your first step is to clone gfp gene, (encoding green fluorescent protein), downstream of the “ON” promoter which is always active, expressing downstream genes. You have a vector, the P ON plasmid, and you’ve isolated a DNA fragment containing a promoter-less gfp gene as well as the tet r gene conferring resistance to tetracycline. The vector carries the lacZ gene encoding ß-Galactosidase which converts the substrate, X-gal, into a blue colored product. It also carries two antibiotic resistance genes: kan r and amp r which r r allow for growth on kanamycin and ampicillin, respectively. The lacZ, kan , and amp genes have their own promoters (not shown). Assume all restriction sites are unique unless shown otherwise. Assume that only similarly cut DNA ends can ligate with each other. You may use more than one enzyme for your cloning. Assume all digestions are complete (no partial digestions). Fragment Sac I Not I Xho I amp r ori Sac I Sal I Eco RI P ON kan r gfp tet r Not I I Sal I Eco RV lac Z Not I Sal I Eco RV Eco RI P tet P ON Plasmid Eco RV Sac I Not a) In order to clone gfp in the correct orientation downstream of P ON...
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