Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
What is a virus? • • • Viruses An agent that causes _______________ in plants and animals Segments of nucleic acids (genetic material like ________ or RNA) contained in a protein coat They are __________ cells Viruses are generally considered to be non-living because they DO NOT have all the characteristics of life. They: 1. DO _______ grow 2. CANNOT maintain homeostasis 3. DO ______ metabolize Viruses are similar to living things in 2 ways: 1. They contain nucleic acid (DNA or RNA) 2. They contain ______________ (in the form of a capsid) Terminology Pathogen- agent that causes disease Host- an organism that _____________ and nourishes something Capsid- the _____________ coat of a virus Envelope- surrounds the capsid and helps viruses enter cells Bacteriophage- a virus that attacks a _____________ Prophage/Provirus- a viral DNA segment inserted into a bacterial cell Retrovirus- a virus that replicates by first transcribing RNA into DNA (HIV) Lysis- the breaking ____________ of the cell to release new viruses Viroid- a single strand of viral RNA that causes __________ diseases Characteristics of a Virus When trying to find the cause of tobacco mosaic disease (disease that stunts the growth of tobacco plants) scientists discovered something other than bacteria was causing TMV Concluded it was _________________ than a bacterium and named it virus after the Latin word meaning “__________________” 1935, Wendell Stanley concluded that TMV was a chemical rather than an organism/cell • Smaller than prokaryotic cells (like bacteria) • Not normally classified (debate over living vs. nonliving) • Live and reproduce ____________ inside other living cells • Cause diseases such as colds, flu, AIDS, smallpox, measles, chicken pox, rabies, mumps, and mononucleosis How are Viruses Structured? • • Viruses have an outer layer called a capsid that is made of ____________ Inside the capsid is ______________ material such as DNA or RNA (but it never contains both as the same time) Structure and Shapes 2 parts to a virus: –Core of nucleic acid (DNA or __________) –Protein coat (capsid) that encases the core of nucleic acid 5 basic shapes of a virus: (draw an example of each below, next to the description) – Helical – Binal – Spherical – Filovirus – Polyhedral • Helical: – RNA or DNA is coiled in a long narrow capsid Ex. Tobacco Mosaic Virus • Spherical: – Typically studded with receptors, may be enveloped Ex. Influenza Virus (Flu) • Polyhedral: – Geometric in appearance Ex. Adenovirus (causes the common cold) Draw: Draw: Draw: • Binal: – Polyhedral capsid – Helical tail Ex. Bacteriophage • Filovirus: – No distinct uniform shape – Threadlike loops Ex. Ebola virus Draw: Draw: HIV a Retrovirus HIV- Human immunodeficiency virus Structure: • ___________________ • Contains RNA • Retrovirus • Exterior wall made of glycoprotein • Binds to human ______________ cells at specific receptor sites Retrovirus • HIV is a special type of virus called a retrovirus • Viruses that get their genetic information copied ________________… – From RNA to DNA • Virus that contains RNA • When the virus infects the cell, they produce a DNA copy of their RNA • Responsible for some types of _________________ in animals Human Diseases Caused by Viruses Category Disease Sexually transmitted disease AIDS (__________), genital herpes Childhood diseases Measles, _____________, chicken pox Respiratory diseases Common cold, influenza (flu) Skin diseases _____________, shingles Digestive tract diseases Gastroenteritis Nervous System diseases Polio, viral meningitis, ___________ Other diseases Smallpox, hepatitis, Avian Bird flu, Ebola, SARS, West Nile What is a Prion? A prion is a ________________ that can cause infection or disease Prions are different from viruses in their composition: - prions consist of protein _____________ while viruses contain nucleic acids and a protein coat And how they replicate: – When mutated prions comes in contact with normal prion it causes the normal prion to change its shape to that of a infected prion. – Like a domino effect Disease Caused by Prions • Abnormal prions infect and burst nerve cells in the brain leaving spaces that make the brain look like a ____________ • Prions cause diseases such as “mad cow.” – Abnormal prions are found in the brains and spinal cords of cattle. Scientists think that spinal cords might be cut during butchering, infecting the meat, and then infecting humans that eat the meat.