A microbiologist is working with two genera of bacteria, A and B, to determine if cells are competent. Strains are grown under optimal conditions, and DNA fragments that carry the gene for green fluorescent protein is added to each culture at 20-minute intervals. Samples from each treatment are plated to nutrient agar and incubated, after which the plates are examined under an ultraviolet lamp. The microbiologist observes that all plates of bacteria B contain colonies that are fluorescent, while for bacteria A only the plates from stationary phase demonstrate fluorescent colonies. What can be concluded from these results?
A. Competence in bacteria A is constitutively expressed.
B. Competence in bacteria B is dependent on the phase of growth.
C. Both bacteria A and bacteria B cells are competent.
D. Neither bacteria A nor bacteria B cells are competent.
Answer: C
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For the process of diffusion to occur, molecules must
A. move from areas of high concentration to areas of lesser concentration until an equilibrium is reached. B. move from areas of low concentration to areas of higher concentration until an equilibrium is reached. C. remain stationary until their molecular motion allows for an equilibrium to be reached. D. move from areas of high concentration to areas of lesser concentration until facilitated transport can assist the molecular equilibrium. E. move from areas of high concentration to areas of lesser concentration until an equilibrium is reached by active transport.
This is the Lophotrochozoan phylum with the most species, having about 100,000 described living
species.
a. Rotifera b. Mollusca c. Platyhelminthes d. Annelida e. Nemertea
Which of the following is a possible advantage for the environment of having farmers use plants that genetically produce Bt toxin?
A) Plants with genes for the toxin are eaten less often by insects, and therefore less insecticide is needed. B) Plants that produce Bt toxin must be grown from new seeds each season, and therefore fewer of them are planted. C) Bt toxin is advantageous to many species of invertebrates that grow in the same fields. D) Harvesting plants with these genes is less disturbing to the soil layers where they are planted. E) Plants with these genes must be sprayed with the organism, but need much less than other plants.
________ is the medication given to combat morning sickness that caused deformed and missing limbs in infants in the late 1950s and early 1960s
A) Thalidomide B) Rubella C) Accutane® D) Alcohol E) Nicotine