The antibiotic rifampicin blocks transcription in many bacteria. In the presence of the antibiotic, adding sigma factor has no stimulating effect on RNA synthesis. A footprinting experiment on a rifamycin treated sample shows that the polymerase remains located at the promoter site in the presence of eNTPs and Mg2 ion. What step of transcription is rifamycin likely to block

Which is an example of a population?

When the cell concentrates potassium within, against the natural tendency of matter, it is performing a.passive diffusion b.facilitated diffusion c.active transport d.pinocytosis

Which of the following observation darwin shape his concept of descent with modification? a) species diversity declines farther from the equator. b) fewer species live on islands than on the nearest continents. c) birds live on islands located farther from the mainland than the bird's maximum nonstop flight distance. d) south american temperate plants are more similar to the tropical plants of south america than to the temperate plants of europe. e) earthquakes reshape life by causing mass extinctions.