Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?
A) Proto-oncogenes first arose from viral infections.
B) Proto-oncogenes normally help regulate cell division.
C) Proto-oncogenes are genetic "junk."
D) Proto-oncogenes are mutant versions of normal genes.
E) Cells produce proto-oncogenes as they age.
Answer: B
Answer: B
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Which of the following statements is not true of early plant evolution, as we have learned from Rhynie cherts?
A. Early vascular plants were small, up to 15 cm tall. B. Early vascular plants branched repeatedly and contained sporangia at their tips. C. The stems of early vascular plants lacked a cuticle or stomata. D. Some of the early plants have a branched sporophyte, but no evidence of vascular tissue. E. Fossils indicate that the roots and leaves of lycophytes evolved independently from those of ferns, horsetails, and seed plants.
In the first experiment to test the pedometer hypothesis in Sahara desert ants, which results did the researchers obtain?
A. Ants with normal legs walked past the home nest, ants with stumps found the nest, ants with stilts were short of the nest B. Ants with stilts walked past the home nest, ants with normal legs found the nest, ants with stumps were short of the nest C. Ants with stumps walked past the home nest, ants with normal legs found the nest, ants with stilts were short of the nest D. None of the above
Where does the primary uptake of water and mineral ions from the soil occur?
a. in the root hairs b. in the pericycle c. in the endodermis d. in the quiescent centre
The definition of a genetically modified organism is an organism carrying a gene that was acquired by artificial means.
a. true b. false