One of the questions early geneticists had to answer was how only four nucleotides can specify placement of 20 amino acids in proteins. Today we know that _________, a sequence of three adjacent nucleotides, determine the insertion of a specific amino acid in a polypeptide chain
a) codon
b) karyotype
c) reverse transcritption
d) glycerol
Answer: a) codon
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Blood in arteries
a. always travels away from the heart. b. travels away from the heart only if it is oxygen rich. c. always travels toward the heart. d. travels from the lungs. e. is always oxygen rich.
The characteristic that enables efficient gas exchange in capillaries is:
a. the very short total length of the capillaries. b. their proximity to the heart. c. thick walls of connective and muscle tissue. d. thin walls that are only one cell wide. e. the long total length of the capillaries.
Microtubules that form the mitotic spindle tend to originate from or terminate in
a. centromeres and telomeres. b. euchromatin. c. centrioles and telomeres. d. the nuclear envelope. e. centrioles and kinetochores.
What was the original purpose of sexual reproduction?
A. to become better adapted to a given environment B. to form more complex organisms C. to repair damaged DNA D. All of the choices are correct.