Are Viruses living? They are both and neither. They have some of properties of life. However they can't maintain a constant internal. Example: Viruses can be killed and they can reproduce. <br><br>
What is a Virus? A virus is a non-cellular particle made up of genetic material and protein that can invade living cells.
Characteristics of Viruses: <br>Nonliving structures <br>Noncellular Contain a protein coat called the capsid <br>Have a nucleic acid core containing DNA or RNA <br>Capable of reproducing only when inside a HOST cell <br>Some viruses are enclosed in an protective envelope <br>Some viruses may have spikes to help attach to the host cell like HIV <br>Most viruses infect only SPECIFIC host cells
Outside of host cells, viruses are inactive <br>Viruses lack ribosomes and enzymes needed for metabolism <br>Use the raw materials and enzymes of the host cell to be able to reproduce
<div>Some viruses cause disease like Smallpox, measles, mononucleosis, influenza, colds, warts, AIDS, Ebola</div><div> Some viruses may cause somecancers like leukemia</div><div>Virus-free cells are rare</div>
Taxonomy of Viruses. <br>1) RNA or DNA Virus <br>2) Do or do NOT have an envelope <br>3) Capsid shape <br>4) HOST they infect
Viruses that attack bacteria are called bacteriophage or just phage<br>
Retrovirus Characteristics Contain RNA, not DNA Family Retroviridae Contain enzyme called Reverse Transcriptase When a retrovirus infects a cell, it injects its RNA and reverse transcriptase enzyme into the cytoplasm of that cell HIV, the AIDS virus, is a retrovirus Feline Leukemia Virus is also a retrovirus
Viruses are very specific as to which species they attack so they are HOST specific Humans rarely share viral diseases with other animals Eukaryotic viruses usually have protective envelopes made from the host cell membrane
<div>There are two viral cycles 1) Lytic Or Virulent Viruses- virus enters host, replicates, and lyses (burst open) occurs causing death of host cell immediately 2) Lysogenic Or Latent Viruses- Some viruses have the ability to become dormant inside the cell. They are called latent viruses. They may remain inactive for long periods of time (years). Later, they activate to produce new viruses in response to some external signal. HIV and Herpes viruses are examples</div>
Latency In Eukaryotes. Some eukaryotic viruses remain dormant for many years in the nervous system tissues. Chickenpox (caused by the virus Varicella zoster) is a childhood infection. It can reappear later in life as shingles, a painful itching rash limited to small areas of the body. Herpes viruses also become latent in the nervous system. A herpes infection lasts for a person’s lifetime. Genital herpes (Herpes Simplex 2). Cold sores or fever blisters (Herpes Simplex1) Viruses make us sick because they kill healthy host cells.
Treatments: Viruses kill Host cells. Vaccine: An attenuated virus is a weakened, less vigorous virus. “Attenuate" refers to procedures that weaken an agent of disease (heating). A vaccine against a viral disease can be made from an attenuated, less virulent strain of the virus. Attenuated virus is capable of stimulating an immune response and creating immunity, but not causing illness Other Virual Treatments. Interferon are naturally occurring proteins made by cells to fight viruses Genetic altering of viruses (attenuated viruses) Antiviral drugs (AZT) Protease inhibitors – prevent capsid formation.<br> Join us as we explain virus structure, the lytic cycle, and the lysogenic cycle! Music used with permission from Adrian Holovaty (