A radioactive isotope has a half-life of 5,000 years. A rock originally contained 16 grams of radioactive isotope, and now contains 4 grams. Approximately how many years old is the rock?
a) 75,000 years
b) 5 million years
c) 3,750 years
d) 10,000 years
e) 15,000 years
Ans: d) 10,000 years
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The source of calcitonin is the
a. pituitary gland. b. adrenal cortex. c. adrenal medulla. d. thymus gland. e. thyroid gland.
The gene encoding apolipoprotein B exists in two isoforms, APOB100 and APOB48. These two forms are produced as a result of
A. alternative splicing. B. tissue-specific expression. C. a gene mutation that results in a stop codon. D. RNA editing.
The glucose-facilitated diffusion transporter can transport glucose
a. into the cell only. b. out of the cell only. c. into or out of the cell. d. only in the presence of ATP.
Which statement about the macronucleus and the micronucleus of ciliates is correct?
A. The micronucleus is formed by fission of the macronucleus. B. The macronucleus is diploid and the micronucleus is haploid. C. The macronucleus forms by the fusion of micronuclei from two different mating types. D. The micronucleus transmits genetic information through mitosis and meiosis, while the macronucleus maintains routine cellular functions.