Why do most individuals have more than one episode of the common cold in a season?
What will be an ideal response?
The common cold can be caused by a number of different viruses, such as adenoviruses, coronaviruses, echoviruses, and paramyxoviruses. However, most colds are caused by the 100+ serotypes of rhinoviruses. Rhinoviruses are extremely infectious; a single virus is enough to cause a cold in 50% of infected individuals. Symptomatic or not, an infected person can spread viruses to the environment in large amounts. People of all ages acquire immunity to the serotypes they have been infected with in the past, but that immunity does not provide protection from infection with other serotypes. In addition, new serotypes are continuously being released into the population by mutations in the RNA of the virus, ensuring that no one can become immune to all rhinoviruses.
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Few genes in all organisms have common evolutionary roots
Indicate whether the statement is true or false.
During DNA replication, an incoming nucleotide is enzymatically joined to the preceding nucleotide by a(n) ________ bond.
A) hydrogen B) ionic C) phosphodiester D) electrostatic
The use of plants to clean up environmental contaminants is called ____
a. photosynthesis b. phototropism c. translocation d. phytoremediation e. transpiration
All living organisms are dependent upon plants because ____
a. plants produce carbon dioxide as a by-product of photosynthesis b. as producers, they form the base of food chains c. they function to prevent erosion and reduce desertification d. they remove oxygen from the atmosphere e. they contribute to the problems generated by the greenhouse effect