In the Gram-staining procedure, the decolorizer is ________.
A. ethanol or acetone
B. iodine
C. crystal violet
D. safranin
Answer: A
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What is the purpose of the P element in the creation of transgenic Drosophila?
A) Efficiently transfer DNA into Drosophila chromosomes. B) Transfer DNA into a specific site in the host chromosome. C) Transfer DNA only into the nuclei of somatic cells. D) Transfer DNA only into primitive eye cells.
Which of the following types of bonds require electrons to be shared between atoms?
a. non-polar covalent only b. polar covalent only c. ionic only d. both polar and non-polar covalent
Many men make antibodies to sperm, resulting in destruction of sperm to the point of sterility. What would be the likely origin of this autoimmune disease?
A. These antibodies are produced as a result of mutations in T lymphocytes, causing them to make large amounts of antibody. B. Antigens on sperm cells are similar to antigens on a variety of bacteria like Streptococcus. After a strep throat caused by Streptococcus, the immune system produces antibodies to streptococcal antigens, which then cross react with sperm antigens and destroy them. C. Since sperm are not made until after puberty, the immune system cannot scan the antigens on the sperm for immune tolerance. After sperm are made and the immune system sees them, they are recognized as foreign. D. T helper cells erroneously identify sperm cells as foreign invaders, triggering the T cytotoxic cells to start killing sperm.
Reproductive isolation often occurs due to
a. geographic separation. b. species incompatibility. c. mutation. d. genetic drift. e. natural selection.