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Unformatted text preview: Bio 120 Midterm 1 1-26-06 KEY Name: ______________________________ 1 Bio 120 Midterm 1 January 26 th 2006 KEY Question 1 Definitions Define the following terms, as used in developmental biology. Use diagrams as necessary; if the term applies to a particular species or animal group, say which. The more specific the definition the better. (a) Define and distinguish the following terms: blastula, blastomere, blastocyst, blastocoel. 20 points. Blastula is the general term for any animal embryo during early cleavage divisions and before gastrulation. Blastomeres are the large cells of a blastula Blastocyst describes the special stage of the mammalian blastula prior to implantation Blastocoel is a general term for any internal hollow (i.e. fluid filled) cavity in a blastula (b) Define and distinguish the following terms: injection chimera, aggregation chimera. 20 points A chimera is any animal formed from cells of two different genetic origins. The two terms below usually refer to mice. Injection chimera is a chimeric mouse formed by injection of cells (usually ES cells) into the blastocoel of a blastocyst stage embryo. The injected cells become part of the inner cell mass. Aggregation chimera is a chimeric mouse formed by aggregation of blastomeres before the blastocyst stage, i.e. before differentiaton of inner cell mass and trophectoderm. (c) Define and distinguish the following terms: zona pellucida, posterior marginal zone, 10 points Area pellucida is the central clear area of the chick blastoderm (sorryquestion was wrong. Zona pellucida is the outer glycoprotein coat of the mammalian egg. Full points for either definition) Posterior marginal zone is the region of cells at the edge of the avian blastoderm that will give rise to the primitive streak. Bio 120 Midterm 1...
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- Winter '04
- Developmental Biology, inner cell mass, Embryo, Mesoderm, Homeobox, Blastula