Related viruses can combine/recombine information if they infect the same host cell. Some viruses are able to integrate into the host DNA and establish a latent (lysogenic) infection HIV is a well-studied system where the rapid evolution of a virus within the host contributes to the pathogenicity of viral infection. Genetic information in retroviruses is a special case and has an alternate flow of information: from RNA to DNA, made possible by reverse transcriptase, an enzyme that copies the RNA genome into DNA. This DNA integrates into the host genome and becomes transcribed and translated for the assembly of new viral progeny. Vocabulary Antibody Inducer receptor Antigen Lytic cycle repressor B-cell Lysogenic retrovirus Cell-mediated immunity Negative feedback reverse transcriptase communication Operon second messenger cyclic AMP (cAMP) Operator signal cascade cytotoxic T-cell Phagocyte signal transduction G-protein linked receptor phagocytosis signal transduction pathway Helper T-cell phosphorylation cascade transcription factor Hormone positive feedback virus Humoral immunity protein kinase white blood cell Thinking Practice Refer to the diagram at the right to respond to the following questions. Is the hormone hydrophobic or hydrophilic? How do you know? hydrophilic-it can’t move through the membrane. Explain how the action of the hormone might be different if it could move through the cell membrane. it could move through the membrane, and be received by receptor inside the cytoplasm. Explain what is happening in this picture and make a prediction what will be the end result in the cell to which this hormone has bound. the hormone triggers a signal transduction pathway, which will trigger a cellular response this response – could be activating a transcription factor that starts to transcribe DNA and eventually thorugh transcription make a protein. Examples could include the protein hormone insulin triggering a response of making a glucose transporter protein that is imbedded in the cell membrane.
Related viruses can combine/recombine information if they infect the same host cell. Some viruses are able to integrate into the host DNA and establish a latent (lysogenic) infection HIV is a well-studied system where the rapid evolution of a virus within the host contributes to the pathogenicity of viral infection. Genetic information in retroviruses is a special case and has an alternate flow of information: from RNA to DNA, made possible by reverse transcriptase, an enzyme that copies the RNA genome into DNA. This DNA integrates into the host genome and becomes transcribed and translated for the assembly of new viral progeny. Vocabulary Antibody Antigen B-cell Cell-mediated immunity communication cyclic AMP (cAMP) cytotoxic T-cell G-protein linked receptor Helper T-cell Hormone Humoral immunity Inducer Lytic cycle Lysogenic Negative feedback Operon Operator Phagocyte phagocytosis phosphorylation cascade positive feedback protein kinase receptor repressor retrovirus reverse transcriptase second messenger signal cascade signal transduction signal transduction pathway transcription factor virus white blood cell Thinking Practice Refer to the diagram at the right to respond to the following questions. Is the hormone hydrophobic or hydrophilic? How do you know? hydrophilic-it can’t move through the membrane. Explain how the action of the hormone might be different if it could move through the cell membrane. it could move through the membrane, and be received by receptor inside the cytoplasm. Explain what is happening in this picture and make a prediction what will be the end result in the cell to which this hormone has bound. the hormone triggers a signal transduction pathway, which will trigger a cellular response – this response could be activating a transcription factor that starts to transcribe DNA and eventually thorugh transcription make a protein. Examples could include the protein hormone insulin triggering a response of making a glucose transporter protein that is imbedded in the cell membrane.
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