Why do harmful agents cause the most severe birth defects during the embryonic period?

A) The mother's hormones are at the highest levels at this time.
B) The embryo has not yet implanted into the uterus.
C) This is the period when substances pass most easily through the placenta.
D) This is a period of rapid differentiation when cells and tissues acquire specific functions and organs form.


Answer: D

Biology & Microbiology

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A. in the vagina. B. in the cervix. C. in the uterus. D. in the fallopian tubes. E. in the ovaries.

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Channels in membranes are best described as:

A. open spaces B. closed spaces C. protein plugs D. molecule catchers E. pores for air exchange

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Which of the following is the correct order of the stages of meiosis?

a. prophase I, metaphase I, anaphase I, telophase I, cytokinesis, prophase II, metaphase II, anaphase II, telophase II, cytokinesis b. prophase I, prometaphase I, metaphase I, anaphase I, telophase I, cytokinesis, prophase II, prometaphase II, metaphase II, anaphase II, telophase II, cytokinesis c. prophase I, metaphase I, prometaphase I, anaphase I, telophase I, prophase II, prometaphase II, metaphase II, anaphase II, telophase II, cytokinesis d. prophase I, metaphase I, prometaphase I, anaphase I, telophase I, prophase II, metaphase II, prometaphase II, anaphase II, telophase II, cytokinesis

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Does the presence or absence of a particular protein correlate with the presence or absence of a particular allele?

a. Yes b. No

Biology & Microbiology