What enzyme is responsible for unwinding the DNA during replication?

a. DNA polymerase
b. DNA ligase
c. helicase
d. primase


c. helicase

Biology & Microbiology

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A scientist reports the isolation of a new blood-borne virus that completely shuts down presentation of viral epitopes on MHC molecules in the cells it infects

He produces an internet video describing it and how it will be indestructible by CD8+ cytotoxic T cells and will kill millions (if not billions) of people.The medical community quickly denounces the dire warning as irrevlevant, and the whole thing is quickly forgotten-why? A. CD8+ T cells are not the cells that are responsible for killing virally infected cells. The terrorist mad scientist is a misinformed idiot. B. While CD8+ T cells ARE important for eliminating a viral infection, they are not the ONLY things that are capable of doing so. Natural killer cells can kill virally infected cells that have shut down MHC antigen presentation, and interferons can assist in cleaning virally infected cells. C. A blood-borne virus would not be capable of rapidly infecting millions of people, due to its difficult mode of transmission. D. B cells would be primed right away to produce complement proteins to destroy the virus. This would prevent cells from being infected with it in the first place. His plot would be foiled. E. While CD8+ T cells ARE important for eliminating a viral infection, they are not the ONLY things that are capable of doing so. Natural killer cells can kill virally infected cells that have shut down MHC antigen presentation, and interferons can assist in cleaning virally infected cells AND a blood-borne virus would not be capable of rapidly infecting millions of people, due to its difficult mode of transmission.

Biology & Microbiology

Air rushes into the lungs of humans during inhalation because

A. the volume of the thoracic cavity increases. B. pressure in the alveoli increases. C. the diaphragm contracts and pushes upward on the chest cavity. D. smooth muscle lining the trachea, bronchi and bronchioles contracts and causes their volume to increase. E. pulmonary muscles contract and pull on the outer surface of the lungs.

Biology & Microbiology

The ____ forms the skeleton of invertebrate chordates

a. pharynx b. neural crest c. oral hood d. notochord e. cranium

Biology & Microbiology

During which cellular process do all three forms of RNA associate?

A. ribosome assembly B. protein synthesis C. chromatin formation D. formation of the nucleolus

Biology & Microbiology