ICQs11,12.ppt

You transfect ES cells from a black mouse (dominant marker) with this construct : Following transfection, the culture will include cells that have lost the transgene without inserting it cells that have inserted the transgene by homologous recombination at the YFG locus cells that have inserted the transgene at another locus by end-joining to a nicked strand followed by DNA repair. 1) In non-selective growth medium (no neomycin or gancyclovir) the most frequent class of cells will be _a__. TK YFG YFG 2) In medium containing gancyclovir alone, the most frequent class of cells will be _a__. Neor ICQs Class 11—everyone who attended received 3 pts for today 3) In medium containing neomycin alone, the most frequent class of cells will be _c__ . 4) In medium containing neomycin and gancyclovir, the most frequent class will be _b__. TK YFG YFG cells that have lost the transgene without inserting it cells that have inserted the transgene by homologous recombination at the YFG locus cells that have inserted the transgene at another locus by end-joining to a nicked strand followed by DNA repair. Neor 5. You inject embryonic stem cells that have undergone homologous recombination at the YFG locus into blastocysts obtained from a mated white mouse and reimplant them into pseudopregnant white females. (Note: these white mice are homozygous black –/black –; black coat color is dominant, and the gene is on a different chromosome from the YFG). When she gives birth to offspring (Po mice): a) all will be variegated (both black and white patches of coat color). b) a few may be white, but the majority will be variegated. c) some will be white, some will be variegated. B—because a mouse could be white if no skin cells were from ES cells 6. You mate a variegated (chimeric) female mouse to a white male, and examine their offspring (F1) for coat color and the presence of the knocked out YFG. Which of the following statements is true? (Remember: the white mice are homozygous black –/black –; black coat color is dominant, and the gene is on a different chromosome from YFG). a) All of the black offspring are homozygous for the transgene (YFG-/YFG-) b) Some of the black offspring are homozygous for the transgene (YFG-/YFG-) c) All of the black offspring are heterozygous for the transgene (YFG-/YFG+) d) All of the black offspring are homozygous normal (YFG+/YFG+) e) Some of the black offspring are heterozygous for the transgene (YFG-/YFG+) E, because the black marker is on a different chromosome, so it’s possible to get black offspring that are YFG +/+ due to normal segregation of chromosomes 1. Which of the following statements best describes the process of fertilization? a) the egg reacts to signals from the sperm. b) the sperm reacts to signals from the egg. c) each of the two gametes reacts to signals from the other. Class 12 ICQs - Fertilization and cleavage 2. Activating the machinery in the sperm acrosomal vesicle first allows the sperm to a) sense presence of and swim toward the egg. b) bind to the outermost surface of the egg. c) penetrate the outer layers of the egg. d) depolarize the egg plasma membrane. 3.* The first thing a sea urchin egg does to prevent polyspermy after a sperm makes contact with the cell membrane is to a) take evasive action to avoid contact with other sperm. b) initiate the cortical reaction and formation of a protective layer with destruction of sperm binding sites. c) lower its membrane potential by allowing influx of Na+ ions. d) raise its membrane potential by pumping out Na+ ions. e) raise its cytoplasmic pH by anti-porting Na+ in and H+ out. 0.5 point 4. Suppose you have activated a sea urchin egg artificially in the absence of sperm and injected an isolated sperm nucleus into it. Will the resulting egg form a zygote and continue development? a) Yes b) No 5. Suppose you do the same experiment with a mammalian egg and sperm nucleus. Will the resulting egg form a zygote and develop? a) Yes b) No 6.* Which of the following statements about what happens during cleavage is FALSE? a) The three orthogonal axes of the embryo and their polarities are established. b) The zygote contents are partitioned into separate cells as the embryo grows in size. c) Some cell identities are determined and certain cells are separated from each other. d) A hollow ball or disc of cells is formed called the blastula. e) Control of development shifts from maternally derived to embryonically produced gene products. 0.5 points 7. The first cleavage in the C. elegans embryo is unequal because: a) factors in the cortex that specify the position of the future cleavage furrow are positioned posterior to the middle of the embryo. b) the spindle is pulled toward the posterior end of the embryo prior to cytokinesis. c) the spindle is pulled toward the anterior end of the embryo prior to cytokinesis. A P 8. Consider a fertilized egg from a species in which the first cleavage is meridional. The default orientation of the second cleavage (in the absence of any mechanism to alter default spindle orientations) will be a) meridional (passing through poles). b) equatorial (perpendicular to A-V axis). c) either meridional or equatorial, cannot predict which.