Name Student ID Zoo 470 Exam 1 Spring 2015 February 25 2015 This exam has a total of 6 pages and a total of 50 points You will have 90 minutes to complete it Please put your name and student ID on all pages Good luck 1 Provide brief definitions for each of the following 4 points a polar body Small product of each of the two female meiotic divisions The oocyte retains virtually all of the cytoplasm whereas the polar bodies have very little cytoplasm b fate mapping Process by which cells in an early embryo are followed to see what progeny they make later in development Fate mapping can involve applying bits of color to the exterior of the embryo simply watching embryos carefully or injection of a tracer into the cytoplasm of individual cells c acrosomal vesicle Vesicle in sperm head containing digestive enzymes and other components The AV fuses with the sperm plasma membrane following the acrosome reaction d transdifferentiation Process by which a differentiated cell can be converted to another differentiated cell Recent work by the Melton lab showed this is possible in the mammalian pancreas 2 MPF and cytostatic factor are known to regulate meiotic cell divisions Answer the following questions based on your knowledge of these factors effects on cell division a If purified CSF were injected into one cell of a two cell embryo immediately after first cleavage what would you predict would happen at the time of the next division Clearly state your reasoning 2 points At the next division the injected cell would arrest at metaphase since CSF would stabilize MPF preventing its breakdown b Recall that frog eggs can be artificially activated by pricking them with a needle initiating the same physiological changes as fertilization What would you expect would happen to levels of MPF within a few minutes after pricking an egg Clearly state your reasoning mentioning specific molecular components where appropriate 2 points Calcium elevation leads to CSF breakdown in such an oocyte quickly leading to MPF inactivation i e decrease in MPF activity via the anaphase promoting complex APC Page 1 Name Student ID 3 You have isolated a gene that you believe encodes a novel sperm cell surface protein headline and you are making a presentation to a major pharmaceutical corporation for research support to work on this protein a You come to the presentation armed with the following pieces of data For each of the following facts state the technique s you used to obtain your data If more than one technique is required list all techniques necessary 3 points Discovery When viewed under the microscope secondary spermatocytes in the human seminiferous tubule express headline mRNA Although you do not possess a C elegans headline mutant you show that headline is required for fertilization in C elegans Prevention of translation of headline protein in male zebrafish results in sperm that cannot fertilize eggs Technique s Used for Discovery In situ hybridization RNAi Morpholinos b headline mutant sperm are inefficient at undergoing the acrosome reaction Suppose you find that headline encodes a calcium channel protein that allows calcium to enter sperm cells when they contact the zona pellucida and the mutants do not make it Describe one experiment that you could perform that would show that if the normal ionic events that trigger the acrosome reaction occur the mutant sperm will undergo a normal acrosome reaction 2 points Treat with calcium ionophore which should trigger calcium elevation even in mutant sperm triggering the acrosome reaction c Headline has multiple roles in development You learn that C elegans headline is a zygotic gene required for embryonic survival If a mother heterozygous for a recessive mutation in headline mates with a father heterozygous for the same mutation what percentage of her offspring would you expect to die 1 point Percentage of dead offspring 25 4 Regulation of reproduction in humans involves a number of secreted factors a For each of the following identify the source of the hormone or factor and the primary tissue s affected by the hormone or factor 2 points Hormone factor gonadotropin releasing hormones follicle stimulating hormone FSH Source Hypothalamus Target Tissue Ant pituitary Ant Pituitary Ovary follicle b The standard birth control pill suppresses ovulation in human females In addition to estrogen the standard birth control pill contains another steroid hormone Based on what you know about the inhibitory effects of hormones during the ovulatory cycle what is this hormone 1 point Hormone progesterone Page 2 Name Student ID 5 Sperm egg binding is crucial for normal development and can be affected by many factors Please complete the following table which asks whether or not a sperm will bind to beads or eggs based on your knowledge of the acrosome reaction and sperm egg interactions in various species 6 points Fertilization yes no no Sperm type Sea urchin sperm not exposed to egg jelly Untreated sea urchin sperm Egg type Sea urchin egg stripped of its egg jelly Reasoning Sperm did not undergo acrosome reaction so no bindin on the surface half credit for saying something about RESACT only Fertilization is species specific In this case bindin from one species won t interact with eggs from another Normal eggs from a different species no Human sperm extracted directly from the seminiferous tubule Sea urchin sperm Human oocyte cumulus complex no The sperm hasn t undergone full maturation capacitation Sea urchin egg held at 70 mV by a voltage clamp yes Fast block can t occur but fertilization will still take place 6 You have identified a new species of ascidian Wisconsinus buckii that is closely related to other well characterized species but with a difference the one celled zygote has a crescent shaped region of red cytoplasm that is inherited by cells that form most of the tail muscles in the tadpole a You believe that the red crescent contains localized determinants for muscle formation Without knowing what molecules are involved in the red crescent s activity describe one experiment that you could perform to show that the red crescent is sufficient for muscle formation 3 points Accepted several answers The textbook answer is the following Use a needle to press on the egg redistributing the red crescent so that some cells inherit some of the crescent material that would not normally Then see if these cells make muscle If they do the red crescent material is sufficient for muscle