practice_book_biology

Practice_book_biology

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Unformatted text preview: (E) Fewer than 12 12 Between 12 and 24 24 More than 24 187. During anaphase, how many kinetochores would be expected in a normal rat kangaroo lymphocyte? (A) (B) (C) (D) (E) 12 18 24 36 48 GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 57 Questions 189-192 Protein X is a protein kinase encoded by mRNA X and is normally present in extracts of whole cleavage-stage frog embryos. Protein I, encoded by mRNA I, is an inactive mutant form of protein X and blocks the function of protein X present in the same cell by competing for binding. The results shown in the table below were obtained in a series of experiments in which all four cells in four-cell-stage embryos were injected as shown and allowed to develop to the early larval stage. Control embryos were pierced by a needle, but no material was injected. The larvae were scored for the presence or absence of eyes in the normal dorsal body axis and for the presence of eyes in the ventrally located secondary body axis that formed as a result of some of the treatments. Material Injected Control mRNA X mRNA I Control mRNA X mRNA I Injection Location Dorsal Dorsal Dorsal Ventral Ventral Ventral Dorsal Body Axis with Eyes 100% 0% 100% 100% 100% 100% Ventral Body Axis with Eyes 0% 0% 0% 0% 0% 100% GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 58 189. The results suggest that protein X has which of the following effects on formation of normal head structures? (A) (B) (C) (D) (E) Weak inhibition Weak stimulation Strong inhibition Strong stimulation The effect cannot be evaluated from these data. 192. In Mangold and Spemann’s experiments pieces of dorsal lip tissue transplanted to the ventral surface of amphibian embryos induced the formation of a secondary body axis. Their results can be reconciled with the results shown above by assuming which of the following about the cells of the dorsal lip of the blastopore (Spemann’s primary inducer) ? (A) They secrete protein X into the extracellular matrix of the embryo. (B) They destroy protein X in the extracellular matrix of the embryo. (C) They contain relatively high concentrations of protein X. (D) They stimulate protein X synthesis or increase activity of protein X in neighboring cells in the embryo. (E) They inhibit protein X synthesis or decrease activity of protein X in neighboring cells in the embryo. 190. The data indicate that in at least some cells in the frog embryos, translation effectively occurs for (A) (B) (C) (D) (E) mRNA X but not mRNA I mRNA I but not mRNA X neither mRNA X nor mRNA I both mRNA X and mRNA I most types of mRNA molecules 191. If translation of mRNA X occurs during cleavage, the results suggest that protein X would most likely be detectable at which location in untreated late-cleavage-stage frog embryos? (A) Primarily in the dorsal cells of the embryos (B) Primarily in the equatorial cells of the embryos (C) Primarily in the ventral cells of the embryos (D) In...
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This document was uploaded on 03/16/2014 for the course BIO 1434 at UT Arlington.

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