Luria and Delbruck grew many liquid cultures of bacteria then spread a small sample of each culture on nutrient agar infused with bacteriophage in separate petri plates. They assayed the number of bacterial colonies that formed on each plate. What did the appearance of a bacterial colony on a petri plate indicate?
A) The bacterial colony was derived from one initial cell that was resistant to infection by the bacteriophage.
B) The bacterial colony was made up of many cells that became resistant to bacteriophage infection independently.
C) A colony formed when a bacterial cell was not resistant to bacteriophage infection.
D) The bacterial cells that made up a colony were resistant to antibiotic.
A) The bacterial colony was derived from one initial cell that was resistant to infection by the bacteriophage.
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An operon is:
A. a gene coding for a repressor protein. B. a region of DNA consisting of the promoter, operator, and coding sequence for structural proteins. C. a region of DNA consisting of the operator and coding sequence for structural proteins. D. a region of DNA consisting of the promoter and operator sequences needed to regulate one or more structural genes. E. a single molecule of RNA coding for more than one protein.
Which hormone directly stimulates spermatogenesis?
a. luteinizing hormone b. follicle stimulating hormone c. oxytocin d. testosterone
The dominant phenotype can be produced by which of the following?
a) Rr only b) Both RR and Rr c) RR only d) Both Rr and rr e) rr only
THe lipid bilayer is not permeable to ____
a. Carbon dioxide b. Lipids c. Oxygen d. Sodium ions