Which of the following contributes to asymmetric cell division in a developing embryo?
A. diffusible molecules secreted from one cell detected by another cell
B. developing gradients of mRNA that define critical axes
C. cell division occurring perpendicular to the mRNA gradient
D. All of the choices are correct.
D
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Based on mortality rates shown in Figure 46.11, which stage of the lime swallowtail life cycle would you expect to be the shortest?
A. the egg stage B. the larval stage C. the pupal stage
The activation of the secondary immune response begins with which of the following?
a. Antibodies b. Killer T-cells c. Memory cells d. Mast cells e. Suppressor T-cells
If a female of this species has one chromosome 12 with a blue gene and another chromosome 12 with an orange gene, and has both number 19 chromosomes with short genes, she will produce which of the following egg types?
A) only blue short gene eggs B) only orange short gene eggs C) one-half blue short and one-half orange short gene eggs D) three-fourths blue short and one-fourth orange short gene eggs
What is the net movement of substances to regions of lower concentration called?
A. Osmosis B. Active transport C. Facilitation D. Diffusion