In the absence of a suitable receptor, which mechanism do viroids use to enter a host cell?
a. attachment to other infectious agents that have the suitable receptors to attach and enter the cell
b. entry through an existing open wound
c. production of hydrolases to dissolve cell walls
d. self-cleavage of RNA into tiny fragments that can passively cross the cell wall, be assimilated into the cell, and reassemble upon entering the cell
Answer: B
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Which of the following is NOT true concerning homeotic genes?
A. They encode transcription factors. B. They are the only types of genes that contain a region of DNA called the homeobox. C. They are found in clusters called complexes. D. A portion of the proteins they encode can bind DNA. E. They activate developmental genes.
Which of the following is NOT one of the functions of vascular tissue in plants?
A. physical support of the plant B. transport of water C. transport of minerals D. transport of organic compounds E. transport of gametes
Peahens prefer to mate with peacocks that have
the brightest and largest tail displays. The peacock’s tail is, in and of itself, a disadvantage to the males. It is large and cumbersome and the males are more easily caught by predators because of it. Given these facts, why isn’t the peacock’s tail selected against by natural selection?
a. peacocks lack the mutations to allow selection to work b. it is working- peacocks are slowly going extinct c. in spite of the disadvantage, peacocks with larger tails leave more offspring d. it is selected against but because a peahen gives birth to so many males, the population is not greatly affected e. this is one of those mysteries of biology
Teratogenic effects of alcohol only occur during the first 12 weeks of pregnancy
a. True b. False