Which of the following is true of the topoisomerases found in bacteria?
A. Type I topoisomerases introduce single-stranded breaks and as a result change the linking number by 1.
B. Type I topoisomerases introduce single-stranded breaks and as a result change the linking number by 2.
C. Type II topoisomerases introduce single-stranded breaks and as a result change the linking number by 2.
D. Type II topoisomerases introduce double-stranded breaks and as a result change the linking number by 1.
E. Type I topoisomerases are the only category that can introduce negative supercoils.
A
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The fact that eggs have the ability to recognize surface proteins on sperm of their own species
illustrates
a. behavioral isolation. b. gametic isolation. c. hybrid breakdown. d. hybrid inviability. e. hybrid sterility.
Which of the following is (are) an example(s) of
prokaryotes? a. all protists b. some fungi c. all algae d. all bacteria e. all of these
Both parents are heterozygous for Tay-Sachs disease (an autosomal recessive disorder). Three children in a row were born with Tay-Sachs disease. What is the chance that a fourth child will have Tay-Sachs disease?
a. 25% b. 50% c. 75% d. 100%
A protein that regulates transcription by binding to the operator is known as the
A. repressor. B. CAP. C. operator. D. operon. E. promoter.