Terms : Hide Images
| 40438897 | size of viruses | 20 nm diameter, smaller than ribosome | |
| 40438898 | virus genome | double or single stranded DNA or RNA (NOT both) | |
| 40438899 | capsid | protein shell enclosing the viral genome | |
| 40438900 | virus genome organization | usually a single linear or circular molecule of nucleic acid, sometimes multiple molecules of nucleic acid | |
| 40438901 | capsid subunits | protein subunits called capsomeres | |
| 40438902 | Viral envelope | some viruses have them, membrane made from the host cell's plasma membrane, helps virus infect host | |
| 40438903 | Viral envelops contain | host cell phospolipids and membrane protein, proteins and glycoproteins of viral origin | |
| 40438904 | bacteriophages | also called phages, viruses that infect bacteria | |
| 40438905 | host range | specific type of cell, tissue, species, or range of species that a virus can intect | |
| 40438906 | Viruses identify host cells by | "lock and key" fit between viral surface proteins and specific receptor molecules outside the cells | |
| 40438907 | How viruses reproduce | use their nucleic acid to code for some proteins and enzymes, but uses the cell's other resources | |
| 40439913 | DNA viruses use | DNA polymerase of the host cell to synthesize new genomes | |
| 40439914 | RNA viruses use | virally encoded polymerases that can use RNA as a template | |
| 40439915 | lytic cycle of phages | stage of infection during which the bacteria lyses and releases the phages that were produced within the cell | |
| 40439916 | virulent phage | reproduces only by a lytic cycle | |
| 40439917 | Bacteria and natural selection | natural selection faocrs bacterial mutants with receptors that are no longer recognized by phages | |
| 40439918 | restriction enzymes | enzymes that cut up foreign DNA when phage DNA enters a bacterium | |
| 40439919 | DNA protects itself from its own restriction enzymes by | DNA methylation | |
| 40439920 | lysogenic cycle | allows replication of the phage genome without destroying the host | |
| 40439921 | temperate phages | capable of using the lytic and lysogenic cycle | |
| 40439922 | temperate phage in research | lambda | |
| 40439923 | prophage | viral DNA that has integrated into the bacterial chromosome | |
| 40439924 | triggers switchover from lysogenic to lytic mode | an environmental signal, such as a certain chemical or high-energy radiation | |
| 40439925 | prophage genes expressed during lysogeny | gene for a prophage transcription-preventing protein, and others | |
| 40439926 | expression of lysogenic genes | may alter the host's phenotype, a phenomenon important for medical significance | |
| 40439927 | stages of the lytic cycle | attachment, entry of phage DNA and degradation of host DNA, synthesis of viral genomes and proteins, assembly, and release (lysozyme is produced, host cell wall and membrane our lysed) | |
| 40439928 | phage assembly | head, tail, and tail fibers | |
| 40439929 | stages of lysogenic cycle | phage DNA integration into bacterial DNA, bacterium reproduction, occasionally heads to lytic cycle | |
| 40440581 | animal virus envelopes | many have glycoprotein projections, virus wraps host cell membrane around them to form the envelope | |
| 40440582 | retrovirus | RNA as genetic material, use reverse transcriptase enzyme to produce DNA, then uses transcription and translation to reproduce. example is HIV | |
| 40440583 | bacteriophages rarely | have an envelope or RNA genome, but animals often have both | |
| 40440584 | provirus | integrated viral DNA, permanent resident of the cell | |
| 40440585 | vesicles transport | envelope glycoproteins to the plasma membrane | |
| 40440586 | proviral genes are transcribed | into RNA molecules, genomes for the next viral generation and as mRNAs for translation | |
| 40440587 | viral proteins include | capsid proteins and reverse transcriptase (made in cytosol) and envelope glycoproteins (made in the ER) | |
| 40440588 | Plasmids | small, circular DNA molecules found in bacteria and yeasts, exist apart form the cell's genome but can replicate independently of it and are occasionally transferred | |
| 40440589 | Transposons | DNA segments that can move from one location to another within the cell's genome | |
| 40440590 | mobile genetic elements | plasmids, transposons, and viruses | |
| 40440591 | viruses originated from | probably evolved after life appeared from naked bits of cellular nucleic acids that moved from one cell to another, perhaps via cell surfaces | |
| 40440592 | vaccine | harmless variant or derivative of a pathogen that stimulates the immune system to mount defenses against the harmful pathogen | |
| 40440593 | anti-viral drugs | try to interfere with viral replication, antibiotics do not work | |
| 40440594 | emerging viruses | appear suddenly or are new to medical scientists (example sars) | |
| 40440595 | epidemics | general outbreaks of a viral disease | |
| 40440596 | most antiviral drugs resemble | a nucleoside, as a result interfere with viral nucleic acid synthesis | |
| 40440597 | causes of emerging viruses | mutation of existing viruses, spread of the virus from one host to another, and global travel and spread of virus within a host group | |
| 40440598 | RNA virus high rate of mutation because | RNA genomes not corrected by proofreading | |
| 40440599 | pandemic | global epidemic | |
| 40440600 | viral genomes and proteins spread through a plant by | plasmodesmata, the cytoplasmic connections that penetrate the walls between adjacent plant cells, virally encoded proteins enlarge the plasmodesmata | |
| 40440601 | viroids | circular RNA molecules, only a few hundred nucleotides long, that infect plants | |
| 40440602 | viroid function | do NOT encode proteins, but can replicate in host plant cells and use host cell enzymes, cause errors in the regulatory systems that control plant growth | |
| 40440603 | prions | infectious proteins which appear to cause a number of degenerative disease in various animal species | |
| 40440604 | prion characteristics | act very slowly and are virtually indestructible | |
| 40440605 | prion infects other proteins by | somehow converting normal protein molecules into misfolded prion versions, example mad cow disease |
