Unformatted text preview: Class 6 in class questions Which of the following statements about what happens during cleavage is FALSE? a) The embryo grows in size as the contents are partitioned into individual cells. b) Some cell identities are determined and certain cells are separated from each other. c) A hollow ball or disc of cells is formed called the blastula. d) Control of development shifts from maternally‐derived to embryonically produced gene products. Which of the following statements correctly characterize epithelial or mesenchymal cells? i. ii. iii. iv. Cells are motile. Cells are similar and regular in shape. Cells can communicate with each other through gap junctions. Cells are not in contact, separated by extracellular matrix. a. i and ii are epithelial, iii and iv are mesenchymal b. ii, ii, iv are epithelial, iii is mesenchymal c. i, ii, iii are epithelial, iv is mesenchymal d. i and iii are epithelial, ii and iv are mesenchymal e. ii and iii are epithelial, i and iv are mesenchymal What, in general, allows cells to move differently in the gastrulating embryo (ie, convergent extension of mesoderm vs. epiboly of the ectoderm)? a. The cells have different DNA response elements, and so respond differently to their environment b. The cells contain different transcription factors that allow them to synthesize different proteins to interact with cytoskeletal components c. It’s all timing: all the cells have the same proteins and cytoskeletal elements, but do different things at different time. Answers for worksheet 1. On your diagram, the upper‐most dot was actually moved up to the grey area at the animal pole. That part of the embryo becomes the non‐neural ectoderm. The entire blue area (marked with E and F) becomes part of the nervous system. 2. In the early gastrulating embryo, the cells marked at the dorsal lip are the future dorsal mesoderm of the animal. They make the head mesoderm and notochord. Thus, the first cells to migrate in make the most anterior notochord and the head. In the mid gastrula, we’re still looking at the dorsal cells—but this is a little open to interpretation. These cells could either make the posterior end of the notochord, or they may be the next “set” of cells to migrate in, which make the so called “paraxial mesoderm”, the somites (which will make primarily muscle; see above diagram). Most likely at this stage, we’re looking at cells that will make somites. In the late gastrula, the cells marked are now part of the “ventral lip” not the dorsal lip. These cells are migrating into the ventral side of the embryo and will make intermediate and ventral mesoderm (kidneys, goands, blood, parts of other organs). ...
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This note was uploaded on 02/25/2010 for the course MCDB 4650 taught by Professor Staff during the Spring '08 term at Colorado.
- Spring '08