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Chapter 19

Chapter Study Questions

Chapter Study Questions


This activity contains 11 questions.

	Match the term described in this chapter to the description that is the best match for it. Using the pull-down menus, match each item in the left column to the corresponding item in the right column. colinearity deep homology in situ hybridization re-purposing, co-opting, or exaptation momeobox genes 1.1 homology in structure that is due to underlying homology in the genes that affect the development of the structure A B C D E 1.2 usage of a pre-existing gene to function in development of a novel characteristic that was not its original purpose A B C D E 1.3 a class of genes involved in signalling to cells during development where they are in in the body, and that share a particular 180-base-pair DNA-binding motif A B C D E 1.4 expression of a series of linked genes in a sequence along locations in the animal, or in a sequence in time, that matches their physical sequence on the chromosome A B C D E 1.5 a technique of determining when and where certain genes are expressed, based on addition of fluorescent DNA that will bind to mRNA made by those genes A B C D E

	The strikingly different morphology of insects, chelicerates, myriapods, and crustaceans is probably due to _________.   changes in timing and location of Hox gene expression different numbers of clusters of Hox genes different numbers of Hox genes per cluster

	Review the evolution of the Hox genes in general terms. Is the complexity of animal body plans related to the number of Hox genes or Hox gene clusters? Explain your answer and give examples.   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

	Which of these statements about vertebrate limb formation are correct?   Cells from the ZPA and AER migrate throughout the limb bud and turn on Hox genes of other cells that they encounter. Hox gene expression remains the same until the stylopod, zeugopod, and autopod are all fully developed. A cell in a vertebrate limb bud "knows" where it is through the relative concentration it experiences of certain proteins that, in turn, are only secreted from certain cells in certain areas of the limb bud. The Sonic hedgehog genes, the FGF-4 and 8 genes, and the Wnt7a gene establish the axes of the limb. These genes are not part of the Hox gene family, but they influence Hox gene expression. Hox genes that originally evolved in the context of specifying the anterior-posterior body axis have been co-opted to coordinate the growth of complex limbs.

	Why are fish fins thought to be homologous to tetrapod limbs?   To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

	Match the gene the description that is the best match for it. Using the pull-down menus, match each item in the left column to the corresponding item in the right column. A non-Hox gene that is important in establishing anterior-posterior axes in every known appendange of bilaterians. One of the very first Hox genes to evolve. Has given rise to many other members of the Hox gene family, via gene duplication. This gene is widely expressed in the thorax of spiders, but not in other arthropods. One of the Hox genes that has been co-opted for use in limb development. This particular one is expressed in the distal part of late limb buds, in tetrapods, but not in fish. In insects, the product of this gene has an alanine-rich region that apparently helps to suppress leg development in the abdomen. 6.1 Antennapedia A B C D E 6.2 Abdominal-B A B C D E 6.3 Hox-3 A B C D E 6.4 Hoxa-11 A B C D E 6.5 Distal-less A B C D E

	Decide if the statements below are correct or incorrect.   The flower homeotic genes are all regulated by a master gene called APETAL. Flowers are composed of whorls that can differentiate into stamens, carpels, sepals, or petals, depending on which homeotic genes are active in each whorl. A knock-out mutation in one of the ABC genes results in a flower that lacks one of the whorls but still has the other three whorls intact and in the usual order. Homeotic mutants show that petals and sepals are modified leaves, while stamens and carpels are modified thorns. A knock-out mutation in one of the ABC genes results in a flower that still has four concentric whorls, but in an abnormal order and with some structures duplicated.

	During development, homeotic loci specify   the locations of cells in time and space. the location of the antennae in fruit flies. the adult structures and functions of developing cells. flowering time in plants.

	Evidence that homeotic loci in vertebrates are homologous to those in invertebrates includes   similarities in how the genes are organized on the chromosome. similarities in DNA sequence. the fact that they descended from a common ancestor. The first and second choices are both evidence that these loci are homologous.

	In Drosophila melanogaster, the "decision" about which type of limb will develop on a given body segment is controlled by the _____ gene(s).   wingless (wg) engrailed (en) HOM Distal-less (Dll)

	The evidence from Panganiban et al's studies that appendage-like outgrowths of the body wall are homologous in all bilaterally symmetric animals is particularly strong because   Dll has the same gene sequence in all taxa analyzed. variation in Dll expression leads to differences in the branching patterns of arthropod limbs. the same pattern of Dll expression was found in a wide range of distantly related taxa. it supports morphological evidence that the limbs of arthropods and tetrapods are structurally homologous.

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