Which statement is true of cephalochordates?

a. They lack pharyngeal slits.
b. They have existed for 500 million years.
c. They have well-developed brains.
d. They are excellent hunters.


b. They have existed for 500 million years.

Biology & Microbiology

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What enzyme is responsible for replicating the ends of chromosomes in a eukaryotic cell?

a. DNA polymerase b. RNA polymerase c. primase d. telomerase

Biology & Microbiology

If thyroid hormone levels are very high in the blood, what hormone level would be low in the blood?

a. parathyroid hormone (PTH) b. calcitonin c. thyroid-stimulating hormone (TSH) d. inhibin e. cortisol

Biology & Microbiology

The chemical group box 1 in the accompanying figure is a:

a. pyrimidine. b. purine. c. phosphate. d. amino acid. e. covalent bond

Biology & Microbiology

Which of the following statements about protein kinase A (PKA) is false?

a. In the inactive state, PKA exists as a tetramer of two regulatory (R) and two catalytic (C) subunits. b. PKA binds a total of four molecules of cAMP, one on each of the four subunits. c. PKA binds a total of four molecules, two molecules on each of the two regulatory (R) subunits. d. Once activated, the catalytic (C) subunits dissociate and activate target molecules.

Biology & Microbiology