Presentation on theme: "21.1 – 1 As you learned in chapter 12, mitosis gives rise to two daughter cells that are genetically identical to the parent cell. Yet you, the product."— Presentation transcript:
1 21.1 – 1As you learned in chapter 12, mitosis gives rise to two daughter cells that are genetically identical to the parent cell. Yet you, the product of many mitotic divisions, are not just a ball of identical cells. Why?
2 21.1 – 1Cells undergo differentiation during embryonic development, becoming different from each other; in the adult organism, there are many highly specialized cell types.
3 21.1 – 2What are the fundamental differences between plants and animals in their mechanisms of development?
4 21.1 – 2During animal development, movement of cells and tissues is a major mechanism, which is not the case in plants. In plants, growth and morphogenesis continue throughout the life of the plant. This is true only of a few types of animal cells.
5 21.2 – 1Why can’t a single embryonic stem cell develop into an embryo?
6 21.2 – 1Information deposited by the mother in the egg (cytoplasmic determinants) is required for embryonic development.
7 21.2 – 2If you clone a carrot, will all the progeny plants (“clones”) look identical? Why or why not?
8 21.2 – 2No, primarily because of the subtle (and not-so-subtle) differences in their environments.
9 21.2 – 3The signal molecules released by an embryonic cell can induce changes in a neighboring cell without entering the cell. How?
10 21.2 – 3By binding to a receptor on the receiving cell’s surface and triggering a signal transduction pathway that affects gene expression.
11 21.3 – 1Why are fruit fly maternal effect genes also called egg-polarity genes?
12 21.3 – 1Because their products, made by the mother, determine the head and tail ends, as well as the back and belly, of the egg (and eventually the adult fly).
13 21.3 – 2If a researcher removes the anchor cell from a C. elegans embryo, the vulva does not form, even though all the cells that would have made the vulva are present. Explain why.
14 21.3 – 2The prospective vulval cells require an inductive signal from the anchor cell before they can differentiate into vulval cells.
15 21.3 – 3Explain why cutting and rooting a shoot from a plant, then planting it successfully, provides evidence that plant cells are totipotent.
16 21.3 – 3A shoot is a differentiated structure, yet some of the cells that make it up are able to differentiate and redifferentiate, forming all of the organs of the new plant.
17 21.4 – 1The DNA sequences called homeoboxes, which help homeotic genes in animals direct development, are common to flies and mice. Given this similarity, explain why these animals are so different.
18 21.4 – 1Homeotic genes differ in their nonhomeobox sequences, which determine their interactions with other transcription factors and hence which genes are regulated by the homeotic genes. These interactions differ in the two organisms, as do the expression patterns of the homeobox genes.