Viruses
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Viruses
Much smaller than bacteria (~ 100nm) Obligate intracellular parasites Consist of DNA or RNA covered in a protein coat Specific in the types of cells they target (e.g. hepatitis – liver cells) Spread by coughs, sneezes but also bites (rabies) insects or cuttings (plant viruses)
Reproduction of viruses Use host cell’s nucleotides Use host cell’s energy (ATP)
Retroviruses Human Immunodeficiency Virus (HIV) Binds to receptors on helper T-cells Injects RNA and reverse transcriptase Builds viral DNA from host nucleotides from which many new RNA are made Viral DNA can be incorporated into host DNA and remain dormant
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