Scientists have found that the lifetimes of mRNAs coding for pair-rule regulatory elements in Drosophila embryos may last only a few minutes. What does this suggest about the overall developmental plan of an animal body?
A) The role of mRNAs is less important than the position of genes in chromosomes.
B) Homeotic genes have greater impact in forming an embryo than mRNA from pair-rule genes.
C) Building an animal body requires a sequence of precisely timed steps.
D) Timing of pair-rule sequence determination is not as important as spatial signaling.
Answer: C
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In four-o'clock plants, red flower color is dominant to white flower color. However, heterozygous plants have a pink color. If a pink-flowered plant is crossed with a white-flowered plant, what will be the phenotypic ratios of their offspring?
A. ¼ red, ½ pink, ¼ white B. All pink C. All white D. ½ pink, ½ white E. ½ red, ½ pink
To a person studying utilization of cage space for lions in a zoo, the most useful data would be expressed by the number
of ____.
a. total lions b. lions per square foot c. lions per cage per room d. cages per zoo e. lions of each age
Refer to the accompanying figure with the lateral line organs of fishes. The structures indicated by label 1 are:
a. hair cells.
b. cupula.
c. stereocilia.
d. sensory neurons.
e. supporting cells.
Cell membranes, muscle cells, and tendons contain ____ proteins and enzymes, and some hormones are ____ proteins.
A. monomer, polymer B. denatured, functional C. structural, regulator D. saturated, unsaturated