Ch 47 HW

Part A - Understanding the experimental design How were the researchers able to independently measure DNA synthesis and RNA synthesis?

Part B - Interpreting the graph Select Figure 2 from the dropdown menu at left (Figure 2) . The graph shows DNA synthesis and RNA synthesis with and without the toxin that prevents cell division. For the DNA data, one straight line represents the general trend for time points 1-5, and another straight line for time points 5-11. What changes in synthesis occur at the end of cleavage, at time point 5?

Part C The researchers hypothesized that the toxin increases diffusion of thymidine into the embryos. What was their reasoning?

Part D Time point 5 corresponds to the 12th cell division, except in the presence of the toxin, which blocks cell division. Do the data support the hypothesis that the timing of the end of cleavage depends on counting cell divisions?

Part E - Drawing conclusions In a separate experiment, researchers disrupted the block to polyspermy, generating embryos with 7 to 10 sperm nuclei. At the end of cleavage, these embryos had the same nucleus-to-cytoplasm ratio as the wild-type embryos, but cleavage ended at the 10th cell division rather than the 12th cell division. What do these results indicate about the timing of the end of cleavage?

Part A The first stage of embryonic development is _____. This process produces _____.

Part A - Differentiating between cleavage, gastrulation, and organogenesis Determine which terms, phrases, and images describe each phase of development. Drag each item to the appropriate bin.

Part B - Gastrulation in a frog embryo Gastrulation is the stage of embryonic development following cleavage. During gastrulation, cell division slows dramatically, and cells are rearranged in a precise way, forming three germ layers. The diagram below illustrates gastrulation in a frog embryo, represented in cross section. Drag the labels to their appropriate locations on the diagram. Use only pink labels for pink targets. Not all labels will be used.

Part C - Organogenesis in a frog embryo Tissue and organ formation begins during the process of organogenesis. Which five of the following statements are true about organogenesis in a frog embryo?

Part A In animal development, which of the following best describes the process of cleavage?

Part B What are the cells created by cleavage called?

Part C Which of the following are the three germ layers contained in the gastrula?

Part D Which of the following stages of development is defined by the three embryonic tissue layers (ectoderm, mesoderm, and endoderm)?

Part E What happens to a cell during the process of differentiation?

Part F A child is born without a fully developed pancreas. He is normal in all other respects, and thus doctors believe that the problem most likely began early in development. During which of the following processes did the original error most likely occur?

Part G True or false? Early animal development progresses through distinct stages: first the production of the zygote through fertilization, then cleavage, then the formation of the gastrula, and then the formation of the blastula.

Part A In sea urchins, the process of fertilization produces a(n) _____.

Part B What is the cortical reaction?

Part C As cleavage continues, a zygote forms into a solid multicellular ball called a(n) _____.

Part D Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called a _____.

Part E The three-layered embryo is the _____.

Part F The _____ eventually develops into the sea urchin's digestive tract.

Part G During gastrulation, invagination occurs at the _____.

Part H In vertebrates, the ectoderm gives rise to the _____.

Part A During gastrulation in frogs, a rod of mesoderm under the dorsal surface forms the _____.

Part B During gastrulation in frogs, cells from the animal pole spread over the embryo and form the _____.

Part C The notochord functions as a core around which mesodermal cells form the frog's _____.

Part D An ectodermal thickening above the frog's notochord forms a _____.

Part E The _____ is(are) formed when the neural folds join and a portion of the neural plate sinks beneath the embryo's surface.

Part F The enlarged anterior portion of the neural tube will develop into a frog's _____.

Part G The posterior portion of the neural tube will develop into the frog's _____.

Part A The mesoderm gives rise to _____.

Part A Embryonic cells especially active in assuring nutritional exchange between a pregnant woman and her embryo are found in the _____.

Part A An embryonic cell that is "totipotent" is one that can _____.