In Drosophila, germ cells develop from pole nuclei isolated from the rest of the embryo at the posterior end. How are they "protected" from the effects of posterior concentrations of zygote-produced mRNAs and proteins?
A) Their genes have unresponsive promoters.
B) The cytoplasm at the pole is separated by a compartmentalizing membrane.
C) The pair-rule, gap, and segmentation genes are not expressed in these cells.
D) Homeotic genes in these cells are inhibited by zygotic genes from the mother.
E) Paternal effects operate on the embryo only in the pole cells.
B
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Diastolic blood pressure measures the ________ .
a. peak of pressure in the aorta b. lowest pressure in the aorta c. lowest pressure in the left ventricle d. lowest pressure in the right ventricle e. highest pressure in the left ventricle
A lower number on the pH scale means a solution is more _______, while a higher number on the pH scale means the solution is more _______.
Fill in the blank(s) with the appropriate word(s).
Skin and mucous membranes are mostly involved in
A. adaptive immunity. B. autoimmunity. C. irregular immunity. D. innate immunity.
Although there are fewer than 14,000 living species of seedless vascular plants, they were the
dominant plants on Earth for nearly 200 million years. Their dominance ended at the end of the Carboniferous period, about
a. 1.5 billion years ago. b. 420 million years ago. c. 250 million years ago. d. 125 million years ago. e. 17 million years ago.