Studies of virulence by the human pathogen Bordetella pertussis, the causative agent of whooping cough, has been shown to be controlled by the bvgAS operon. Induction of virulence-related genes only occurs when B. pertussis is grown at 37°C and certain bvgS mutations result in a loss of the temperature response. DNA sequence analysis indicated that the bvgS gene product contains a potential membrane spanning region. In addition, all bvgA mutants incapable of causing virulence had an aspartate residue changed to alanine. Based on this information propose a model for how bvgA and bvgS play a role in B. pertussis virulence.

answer: carbon 14 can only be used to determine the age of the organisms that were once living, and igneous rocks are non living.

explanation:

carbon 14 dating is used to determine the age of the sample by estimating the amount of carbon 14 present in the sample and then comparing it with a reference standard.carbon 14 is a isotope of carbon which is radioactive and unstable. carbon 14 is assimilated by all plants and animals throughout their life from carbon dioxide. however, one the organisms die they stop this assimilation and the carbon 14 content starts to decrease.by knowing how much of carbon 14 is left in an organism after his death, one can estimate the age of the organism. the materials whose age can be estimated by carbon 14 method are the organic compounds. however, some inorganic compounds such as aragonite   shell can also be dated.however, if we consider the igneous rocks it is a non living component which never accumulated carbon 14 in it and thus, we cannot use carbon 14 dating method to estimate its age.