Ex06_S11-Analysis

Ex06_S11-Analysis - Excerpts from Dr. Colavitos Lecture...

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Group Members: _______________________________________________________________Date: ___________ LI ______________________ Unique __________ Day: __________ Room: _______ Lab Start Time ________ BIO206L Spring 2011 Exercise 6 Analysis To be completed as a group and turned in at the beginning of your next laboratory period. Include your “Data & Results”, sketches, acquired digital images, etc. as directed by your laboratory instructor. Show your work for all calculations and/or print your MS Excel data sheets. Be sure to include proper units where necessary. Adhere to University’s Honor Code and course policies. Balance between brevity and completeness. 1. Sketch a rough drawing of sperm surrounding a sea urchin egg and the formation of a fertilization membrane. How long a period of time was required after addition of sperm for a fertilization membrane to form? Sketch a drawing of the first cleavage. How long a period of time was required after fertilization for this cleavage to occur? The fertilization membrane is a vitelline envelope (jelly coat) that formed on the surface of plasma membrane of sea urchin. The membrane is filled with water due to the osmolarity of high concentration of polysaccharides released from cortical granules. The fertilization membrane serves the purpose of preventing other sperms from fertilizing the same egg (block polyspermy). The fertilization membrane takes about 2-5 minutes to form after fertilization in the sea urchin. About 50-70 minutes after fusion of egg and sperm, the zygote undergoes the first cleavage. 2. Discuss the major stages of sea urchin development with reference to your series of detailed drawings and observational notes. How did the embryonic cells compare in size with the original gamete cells? State reasons such a difference might exist. Compare and contrast these very early stages of sea urchin development with that of a human embryo. The fertilization of sea urchin egg and sperm is external. The following are the major stages of sea urchin development after fertilization: The formation of fertilization membrane occurs between 2-5 minutes after the sperm successfully fused with the egg. This occurs to prevent other sperms try to get in the egg (polyspermy) and also it is an indication that the fertilization stage is completed. The fertilization forms the nucleus of the diploid zygote. Upon the fertilization, the egg releases cortical granules, which includes the enzyme and polysaccharides that make the membrane and also separating from the plasma membrane. With the higher concentration of polysaccharides, the membrane draws in water from the outside. The membrane formed around the egg surface first looks like bubbles then gradually balloons out due to osmolarity. It looks clear jelly-like membrane. Within an hour of fertilization, the zygote begins to undergo first cleavage. The
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This note was uploaded on 04/04/2012 for the course ECO 304K taught by Professor Hickenbottom during the Spring '10 term at University of Texas.

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Ex06_S11-Analysis - Excerpts from Dr. Colavitos Lecture...

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