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LAB 7
MICROSCOPIC EXAMINATION OF FERTILIZATION AND CLEAVAGE I. Introduction Developmental biology is a field of study that is relatively new. Traditionally the study of embryonic development was just called “embryology”. Labs associated with these embryology courses consisted exclusively of looking at slides of embryonic development. Although modern developmental biology labs utilize a number of procedures, it is still necessary to be able to identify embryonic structures microscopically. Today’s lab will involve the examination of stages of early development of a number of different organisms. We will show a short film on development, and you should take a look at several websites that have film clips and images. You will also examine prepared slides of fertilization and early cleavage stages of the sea urchin and frog. This work is important for a number of reasons. First it will give us the anatomical background to study fertilization and early development in vivo or in the live animal. Second it will give you a chance to see just what the embryos actually look like, compared to the often cryptic drawings I provide during lectures. II. Procedures You will be using Mathews Atlas of Descriptive Embryology as a guide for today’s lab. Below is a list of the figures and the structures you should be able to identify: Figures 27-36, 43-51: Sea Urchins primary oocyte Fertilized egg Nucleus, nucleolus Blastula, blastomerse, blastocoele Gastrula, blastopore, archenteron Figures 83-90; Amphibians Early cleavage stages Animal and vegetal poles Micromeres and macromeres Blastocoele and archenteron Dorsal lip of the blastopore Finally, below are a few sites for film clips or timelapse images of cleavage are available: Sea Urchin Cleavage Timelapse: http://www.luc.edu/depts/biology/dev/1-4cell.htm Sea Urchin Slides: http://www.bio.rutgers.edu/~gb102/lab_7/701bm-earlycl.html Zebrafish Cleavage: http://www.luc.edu/depts/biology/dev/zebra.mov Xenopus Cleavage: http://www.luc.edu/depts/biology/dev/cleavage.mov
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