Juxtacrine communication uses the circulatory system.
a. true
b. false
Answer: b. false
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You are working in a Drosophila lab, and find a larva with two anterior ends. Both a normal larva and the mutant larva are shown below. What is the most likely explanation for the mutant larva phenotype?
A. There is a mutation in the bicoid gene causing no functional Bicoid protein to be made.
B. The nurse cells that produce the Bicoid protein are defective, so there is no protein at either end of the embryo.
C. There is a mutation in a homeotic gene.
D. There is a high concentration of the Bicoid protein at both ends of the mutant embryo.
E. A protein encoded by a segment polarity gene is not degraded correctly and accumulates in both ends of the embryo.
In humans, the gonads ____
a. produce gametes only b. secrete hormones only c. nourish the embryo only d. produce gametes and secrete hormones only e. produce gametes, secrete hormones, and nourish the embryo
In seed plants, the microspores become ___
a. ovules b. seeds c. pollen grains d. cones e. sperm cells
Schleiden and Schwann stated the "cell theory," which in its modern form says
A. all cells will arise spontaneously, all cells require oxygen, and all cells are composed of one or more cells. B. all organisms are composed of one or more cells, all cells arise spontaneously, and all cells vary in size and shape. C. all organisms are composed of one or more cells, all cells are the smallest living things, and all cells arise by division of other cells. D. all organisms are composed of one or more cells, all cells require oxygen, and all cells arise by division of other cells.