An atom has 19 protons, 19 electrons, and 20 neutrons; what is its atomic mass number?
A) 19
B) 20
C) 38
D) 39
E) 58
Answer: D) 39
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Which of the following statements is correct regarding chromosomes in a eukaryotic cell?
A. Chromosomes are strands of RNA, tightly wrapped up, that are in the cytoplasm. B. Chromosomes are strands of DNA, tightly wrapped up, that are located in the nucleus. C. Chromosomes are strands of RNA, loosely wrapped up, that are located everywhere in the cell. D. Chromosomes are strands of DNA, tightly wrapped up, that are located everywhere in the cell.
AIDS, or acquired immunodeficiency syndrome, is caused by ________.
A. a virus B. a protozoan C. a bacteria D. a fungus
A sperm cell's acrosome ________
A) contains the sperm's nucleus and is the part of the sperm that enters the egg during fertilization B) fuses with the plasma membrane of the egg cell C) contains enzymes that are released when the sperm encounters an egg and dissolves a hole in the jellylike matrix that surrounds the egg D) contains the sperm's mitochondria
Stabilizing selection would be present if
A. gene frequencies do not change from one generation to the next. B. mutations constantly replace the genes lost from one generation to the next. C. there are no selecting agents. D. All of these are possible.