Over the past several decades, populations of Staphylococcus aureus (a type of bacteria that infects wounds) have become resistant to penicillin. You run the following experiment:
As mentioned above, resistance to penicillin is a different biological mechanism than
resistance to antibiotic X. What is the probable origin of antibiotic X resistance in these cells?
A. The cells probably developed resistance to
antibiotic X by undergoing mutation when
exposed to the drug, and thus survived the
exposure.
B. A small percentage of the cells had preexisting
mutations that confer resistance to
antibiotic X. These cells survived exposure to
the drug.
C. Either of the other two options could be
correct because both happen often in nature.
More information is needed to answer the
question.
B
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The production of large quantities of a particular DNA sequence is known as gene ________.
Fill in the blank(s) with the appropriate word(s).
What is the complement DNA strand to 5?-ATTCGGTGA-3??
A. 5?-TAAGCCACT-3? B. 3?-CGGATTGTC-5? C. 5?-CGGATTGTC-3? D. 3?-TAAGCCACT-5? E. 3?-ATTCGGTGA-5?
Starting from the outside and moving in toward the center, which gives the correct order of tissues in
the stem of a young tree?
a. secondary phloem, primary phloem, primary xylem, secondary xylem b. primary xylem, secondary xylem, secondary phloem, primary phloem c. primary phloem, secondary xylem, secondary phloem, primary xylem d. secondary phloem, primary xylem, secondary xylem, primary phloem e. primary phloem, secondary phloem, secondary xylem, primary xylem
Which statements about the complement system of vertebrates are correct? (Check all that apply.)
_____ The complement system is a part of the immune system of vertebrates. _____ The complement system consists of approximately 30 different proteins that circulate in the plasma. _____ If these proteins encounter the cell wall of a bacteria or fungi they form aggregations and eventually produce a pore that leads to the destruction of the invading cells. _____ Although complement proteins attack invaders, they are not involved with histamine release. _____ The complement system produces antibodies to bind invading cells.