Oxygen did not accumulate in the early atmosphere until it reacted with reduced materials, especially ________, in the oceans
A) hydrogen
B) elemental sulfur
C) ferrous iron
D) nitrate
Answer: C
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Some members of the Thermoplasmatales can grow at pH levels below
A) 4. B) 7. C) 0. D) 10.
Which of the following organs of the endocrine system secretes thyroxine and calcitonin?
a. pituitary gland b. pancreas c. hypothalamus d. adrenal glands e. thyroid gland
Base analogs may cause mutations because
A) they modify the chemical structure and properties of the normal base. B) they insert themselves between adjacent bases on the DNA strand and cause an extra base to be inserted during replication. C) they remove amino groups from bases, causing them to pair with the wrong base during replication. D) they may exist in alternate chemical states that pair with different DNA bases than the normal state during replication. E) Both A and C
In trying to determine whether DNA or protein was the genetic material, Hershey and Chase made use of which of the following facts about these two types of molecules?
A. DNA contains phosphorus, whereas protein does not. B. DNA contains nitrogen, whereas protein does not. C. DNA contains sulfur, whereas protein does not. D. DNA contains purines, whereas protein includes pyrimidines.