18.1 Section Objectives – page 475

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18.1 Section Objectives – page 475. Section Objectives: 18.1. Identify the different kinds of viruses and their structures. Compare and contrast the replication cycles of viruses. Section 18.1 Summary – pages 475-483. You’ve probably had the flu—influenza—at some time during your life. - PowerPoint PPT Presentation

Text of 18.1 Section Objectives – page 475

  • 18.1 Section Objectives page 475Identify the different kinds of viruses and their structures.Section Objectives: 18.1Compare and contrast the replication cycles of viruses.*

  • Section 18.1 Summary pages 475-483Youve probably had the fluinfluenzaat some time during your life.Viruses are composed of _____ ______ enclosed in a ______ coat and are smaller than the smallest bacterium.Nonliving particles called _______ cause influenza.*

  • Section 18.1 Summary pages 475-483Most biologists consider viruses to be _______ because they dont exhibit all the ______ for life.They dont carry out respiration, grow, or develop. All viruses can do is _______make copies of themselvesand they cant even do that without the help of living cells.A cell in which a virus replicates is called the _____cell.*

  • Section 18.1 Summary pages 475-483Viruses, such as _____ viruses and _____ viruses, were named after the diseases they cause.Other viruses were named for the _____ or ______ they infect.*

  • Section 18.1 Summary pages 475-483Today, most viruses are given a ______ name ending in the word virus and a ______ name.However, sometimes scientists use ____ numbers to distinguish among similar viruses that infect the same ____.A virus that infects a bacterium is called a __________ (bak TIHR ee uh fayj), or phage for short.*

  • Section 18.1 Summary pages 475-483A virus has an inner core of nucleic acid, either ___ or ___, and an outer protein coat called a ____.CapsidNucleic acidEnvelope*

  • Section 18.1 Summary pages 475-483Some relatively large viruses, such as human ___ viruses, may have an additional layer, called an _______, surrounding their capsids.CapsidNucleic acidEnvelope*

  • Section 18.1 Summary pages 475-483Envelopes are composed primarily of the same materials found in the ______ membranes of all cells.CapsidNucleic acidEnvelope*

  • Section 18.1 Summary pages 475-483___ nucleic acid is either DNA or RNA and contains instructions for making copies of the virus.Some viruses have only four _____, while others have hundreds.Nucleic acidCapsid*

  • Section 18.1 Summary pages 475-483The _____ _____ virus has a long, narrow _______ shape.Nucleic acidCapsid*

  • Section 18.1 Summary pages 475-483The arrangement of _____ in the capsid of a virus determines the viruss _____.Nucleic acidCapsid________ viruses resemble small crystals.*

  • Section 18.1 Summary pages 475-483The protein arrangement also plays a role in determining what cell can be _______ and how the virus infects the cell.Nucleic acidCapsid*

  • Section 18.1 Summary pages 475-483Before a virus can replicate, it must ____ a host cell.A virus recognizes and ______ to a host cell when one of its ______ interlocks with a molecular shape that is the ______ site on the host cells plasma membrane.*

  • Section 18.1 Summary pages 475-483A protein in the ___ fibers of the bacteriophage __ recognizes and attaches the T4 to its bacterial host cell.CapsidNucleic acidTailTail fiber*

  • Section 18.1 Summary pages 475-483In other viruses, the attachment protein is in the ____ or in the envelope.CapsidNucleic acidTailTail fiber*

  • Section 18.1 Summary pages 475-483Each virus has a ________ shaped attachment protein. Therefore, each virus can usually attach to only a few kinds of cells.In general, viruses are species specific, and some also are ____-type specific. For example, polio viruses normally infect only intestinal and nerve cells.*

  • Section 18.1 Summary pages 475-483The species specific characteristic of viruses is significant for controlling the spread of _____ diseases.*

  • Section 18.1 Summary pages 475-483Once attached to the plasma membrane of the host cell, the virus _____ the cell and takes over its ________.Only then can the virus ________.Viruses have ____ways of getting into host cells.*

  • Section 18.1 Summary pages 475-483The virus may _____its nucleic acid into the host cell like a syringe injects a vaccine into your arm.The _____ of the virus stays attached to the outside of the host cell.An ________ virus enters a host cell in a different way.*

  • Section 18.1 Summary pages 475-483After attachment, the plasma membrane of the host cell surrounds the virus and produces a virus-filled vacuole inside the host cells cytoplasm.Then, the virus bursts out of the vacuole and releases its nucleic acid into the cell.*

  • Section 18.1 Summary pages 475-483Once inside the host cell, a viruss genes are _________ and the substances that are produced take over the host cells genetic material.The ____ genes alter the host cell to make new viruses.*

  • Section 18.1 Summary pages 475-483Nucleic acidBacterial host cellBacteriophageBacterial DNAB. EntryThe bacteriophage injects its nucleic acid into the bacterial cell.A. AttachmentC. ReplicationD. AssemblyE. Lysis and ReleaseThe hosts metabolic machinery makes viral nucleic acid and proteins. New virus particles are assembled. The host cell breaks open and releases new virus particles. *

  • Section 18.1 Summary pages 475-483The host cell uses its own _______, raw materials, and energy to make copies of viral genes that along with viral proteins are assembled into new viruses, which _____ from the host cell, killing it.*

  • Section 18.1 Summary pages 475-483The new viruses can then infect and kill other host cells. This process is called a ____ (LIH tik) _____.*

  • Section 18.1 Summary pages 475-483Not all viruses ____ the cells they infect.Some viruses go through a ________ cycle, a replication cycle in which the viruss nucleic acid is ________ into the host cells chromosome.*

  • Section 18.1 Summary pages 475-483A ________ cycle begins in the same way as a lytic cycle.However, in a lysogenic cycle, instead of _________ taking over the hosts genetic material, the viral DNA is integrated into the host cells chromosome.*

  • Section 18.1 Summary pages 475-483Many disease-causing ______ have lysogenic cycles.Three examples of these viruses are ____ _____ I, herpes simplex II that causes ______ herpes, and the _______ B virus that causes hepatitis B.*

  • Section 18.1 Summary pages 475-483Another lysogenic virus is the one that causes _____ ___.*

  • Section 18.1 Summary pages 475-483Having chicken pox, which usually occurs before age ten, gives lifelong protection from another infection by the ___. However, some chicken pox viruses may remain as _________ in some of your bodys nerve cells.*

  • Section 18.1 Summary pages 475-483Later in your life, these proviruses may enter a lytic cycle and cause a disease called _______a painful infection of some nerve cells.*

  • Section 18.1 Summary pages 475-483Either lysis, the bursting of a cell, or ______, the active transport process by which materials are expelled from a cell, release new viruses from the host cell.*

  • Section 18.1 Summary pages 475-483In exocytosis, a newly produced virus approaches the inner surface of the host cells _______ membrane.The plasma membrane surrounds the virus, enclosing it in a _____ that then fuses with the host cells plasma membrane.Then, the ______are released to the outside.*

  • Section 18.1 Summary pages 475-483Many viruses, such as the _____ _______________ ____(HIV) that causes the disease AIDS, are RNA virusesRNA being their only nucleic acid.HIV virus*

  • Section 18.1 Summary pages 475-483Once inside a human host, HIV infects _____ blood cells.Newly made viruses are released into the blood stream by ________ and infect other white blood cells.Normal white blood cells*

  • Section 18.1 Summary pages 475-483Infected host cells still function normally because the viral genetic material is a ______ that produces only a small number of new viruses at a time.Because the infected cells are still able to function normally, an infected person may not appear _____, but they can still ____ the virus in their body fluids.*

  • Section 18.1 Summary pages 475-483Most people with an HIV infection eventually get ____ because, over time, more white blood cells are infected and produce new viruses.Because white blood cells are part of a bodys ______-fighting system, their destruction interferes with the bodys ability to protect itself from organisms that cause disease, a symptom of AIDS.*

  • Section 18.1 Summary pages 475-483Some viruses have been linked to certain ______ in humans and animals.These viruses disrupt the normal growth and division of cells in a host, causing abnormal growth and creating _______.*

  • Section 18.1 Summary pages 475-483Researchers have recently discovered some particles that behave somewhat like viruses and cause infectious diseases.Prions are composed of proteins but have no nucleic acid to carry genetic information.*

  • Section 18.1 Summary pages 475-483Prions are thought to act by causing other proteins to fold themselves incorrectly, resulting in improper functioning.Prions are responsible for many animal diseases, such as mad cow disease and its human equivalent, Creutzfeldt-Jakob disease.*

  • Section 18.1 Summary pages 475-483Viroids are composed of a single circular strand of RNA with no protein coat.Viroids have been shown to cause infectious diseases in several plants.The amount of viroid RNA is much less than the amount found in viruses.*

  • Section 18.1 Summary pages 475-483The first virus to be identified was a plant virus, called tobacco mosaic virus, that causes disease in tobacco plants.Tobacco mosaic virus causes yellow spots on tobacco leaves, making them unmarketable.*

  • Section 18.1 Summary pag