Chapter 46, Problem 7
How do spermatogenesis and oogenesis in humans differ with respect to numbers of cells produced, gamete size, and timing of the second meiotic division?
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Summarize the experimental evidence that Daphnia require three cues to trigger sexual reproduction. Discuss what these cues indicate about the environment.
Many frogs and mice are similar in size, yet a frog egg is vastly larger than a mouse egg. Propose a plausible explanation for this difference in the egg size.
What is the connection between genetic regulatory cascades and the observation that differentiation is a step-by-step process?
Which of the following provides the strongest evidence for the conservation of tool-kit genes? a. Bicoid moved from one fly embryo into the posterior of another fly embryo causes the formation of two head regions. b. Mutation of an unrelated gene in another species of fly has a similar effect to mutation of bicoid in Drosophila. c. A mouse Hox gene can be used to take over the function of a mutated Drosophila Hox gene. d. Sheep can be cloned by fusing a differentiated adult cell with an enucleated egg.
Give examples of negative and positive feedback in hormonal control of the human menstrual cycle. Why can a high estradiol level be considered a 'readiness' signal from a follicle?
Imagine a situation in which a morphogen has its source at the posterior end of a Drosophila embryo. Every 100 µm from the posterior pole, the morphogen concentration decreases by half. If a cell required 1/16th the amount of morphogen found at the posterior pole to form part of a leg, how far from the posterior pole would the leg form? a. 100 μm b. 160 μm c. 400 μm d. 1600 μm