As many as one-half of Earth's plants
A. may already have gone extinct in the last 100 years.
B. may be threatened with extinction at present.
C. may be considered invasive species.
D. are known to be medicinally useful.
E. have been shown to be keystone species.
B. may be threatened with extinction at present.
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A chromosome that has a centrally-placed centromere is called ____________________
Fill in the blank(s) with correct word
Researchers trying to cure a deadly virus have discovered that it can only infect cells that display specific carbohydrate chains on their exterior plasma membrane. An early drug trial incorporated an enzyme designed to digest all carbohydrates outside the cell. Researchers believed that without those carbohydrate markers, the virus would not be able to identify vulnerable cells. When tested, the drug caused massive tissue damage instead. What mistake did the researchers make?
a. They forgot that the primary component of plasma membranes is carbohydrates; the drug destroyed the cells’ membranes. b. Without their carbohydrate markers, the cells were identified by antibodies as being foreign and were destroyed. c. Carbohydrates attached to the plasma membrane also bind cells together; without them, the tissues fell apart. d. The enzymes released carbohydrates into the intercellular medium, allowing the virus to replicate faster.
In the decolorizing step of the Gram stain, which reagent is used?
a. Alcohol-acetone b. Malachite green c. Iodine d. Crystal violet
Which stage of animal virus replication may be blocked by a drug that binds with the viral spike?
A) assembly B) attachment C) replication D) penetration E) uncoating