Chap Viruses

Transcription

1 Honors Biology Study Guide Viruses Name Chap Viruses 1. Viruses are not considered living organisms; rather they are often referred to as acellular parasites. Explain. WHAT ARE THE THREE BASIC PARTS OF A VIRUS: Viral Part Description / Function 2. Which of these parts is not present in all viruses? A BACTERIOPHAGE REPLICATION CYCLE 3. What are bacteriophage (phage is short for bacteriophage)? Give an example of a bacteriophage. 4. What are the two possible replication cycles of a bacteriophage? Label the diagram below, illustrating the 2 possible replication cycles. 5. Define prophage.

2 ANIMAL VIRUSES 8. Most animal viruses have an outer envelope embedded with glycoproteins. What is the function of the envelope and its associated glycoproteins? 9. Animals viruses can either contain RNA or DNA as the nucleic acid. List examples of RNA-containing animal viruses. List examples of DNA-containing animal viruses. REPLICATION CYCLE OF AN ENVELOPED RNA VIRUS 10. Listed below are the steps in the replication of viruses with envelopes. Match the description with the correct step, using Figure as a reference. (Note these are not necessarily in sequential order try to put them in order!) Glycoprotein spikes attach to receptor sites on host cell membrane Envelope fuses with host cell membrane entire virus enters cytoplasm of host cell New capsids surround viral genomes; new viruses bud off cell surface; virus surrounded with modified cell membrane Cellular enzymes remove protein capsid from around viral DNA Viral RNA polymerase replicates viral RNA; viral mrna transcribed and translated A. Assembly and release B. Attachment C. Entry D. Viral RNA and protein synthesis E. Uncoating 11. Explain how the common cold results in less damage than the poliovirus. EMERGING VIRUSES 16. What are the three processes that contribute to the emergence of new viruses? 17. Explain why we require yearly flu shots, whereas viral diseases such as measles and polio require a single vaccination?

3 REPLICATION CYCLE OF THE HIV RETROVIRUS 12. How is the replication of retroviruses different from that of other viruses? 13. What is the function of reverse transcriptase? 14. Listed below are the steps in the replication of a retrovirus. Put the steps in the correct order. Attachment of virus Reverse transcription Viral RNA used as template to produce strand of DNA Uncoating of single-stranded RNA genome Proviral DNA transcribed into mrna; mrna translated into proteins and may become genome for next generation of viruses. Capsid proteins enzymatically removed. Virus enters host cell cytoplasm Integration newly produced viral DNA enters nucleus, inserts into host DNA and becomes provirus. 15. How is replication of HIV retrovirus analogous to lysogenic cycle of a bacteriophage infection?

4 Practice Questions 1) In the lysogenic cycle, new viral particles are. (10.17) a) constantly packaged and produced b) packaged and released when triggered by radiation, chemicals, or other environmental signals c) spontaneously packaged and released d) produced at a very slow rate that is almost undetectable 2) Before an RNA virus is assembled and leaves the cell, a number of processes occur. Place these steps into the order in which they occur: (10.18) 1. Viruses cloak themselves in the host cell's plasma membrane. 2. Viral glycoproteins attach to receptor proteins on the cell membrane. 3. Viral genome RNA is synthesized. a) 2, 3, 1 b) 3, 1, 2 c) 3, 2, 1 d) 2, 1, 3 3) HIV and phage lambda both. (10.17 and 10.20) a) have an RNA genome b) use reverse transcriptase to replicate c) derive their viral envelopes from the host's cell membrane d) integrate their DNA into the host's chromosome 4) During the lytic cycle, but not the lysogenic cycle,. (10.17) a) a phage uses the host cell's "machinery" to produce its proteins b) a phage injects DNA into the host cell c) a prophage is replicated during binary fission d) whole viruses leave the host cell to infect other cells 5) A typical animal RNA virus has an outer membrane envelope that helps the virus enter and leave the host cell. What makes up this outer membrane envelope? (10.18) a) The viral genome serves as mrna for the synthesis of membrane phospholipids. b) The virus coats itself in the host cell's plasma membrane. c) The envelope comes from the host cell's nuclear membranes. d) The outer membrane envelope contains viral RNA, which serves as the genome for the virus. 6) Emerging viruses can originate from. (10.19) a) lambda viruses that were previously confined to bacterial populations that can now spread due to technological changes b) a rapidly mutating lytic phage c) mutations of viruses to prophages d) a virus spreading from one host species to another 7) HIV enters a white blood cell and then uses to make copies of its genetic material. Once HIV proteins have been translated, the virus can be released by. (10.20) a) a virally encoded reverse transcriptase a process known as budding, in which the virus coats itself in the host cell's plasma membrane b) a virally encoded RNA polymerase a process known as budding, in which the virus coats itself in the host cell's plasma membrane c) the host cell's RNA polymerase a process known as cell lysis, in which the virus coats itself in host plasma membrane d) a specific enzyme found in the host cell known as reverse transcriptase a process known as cell lysis, in which the virus coats itself in host plasma membrane

5 8) When a bacteriophage infects an E. coli cell, what part of the phage enters the bacterial cytoplasm? (10.17) a) only nucleic acid b) the coat and its enclosed nucleic acid c) the whole phage d) the cell wall 9) The phage reproductive cycle that kills the bacterial host cell is known as a cycle. (10.17) a) lysogenic b) replicative c) transcriptional d) lytic 10) A prophage is a(n). (10.17) a) type of retrovirus b) viral genetic material that has been incorporated into a bacterial cell's chromosome c) emerging virus d) virus that infects bacteria 11) In the lytic life cycle of phages,. (10.17) a) the viral coat is assembled according to the genetic information of the bacterium b) phage DNA is incorporated into the host cell's chromosome c) the nucleic acid of the phage is all that enters the host cell d) the entire phage is taken into the bacterium 12) A microbiologist analyzed chemicals obtained from an enveloped RNA virus similar to a mumps virus that infects monkeys. He found that the viral envelope contained a protein characteristic of monkey cells. Which of the following is the most likely explanation? (10.18) a) The virus forced the monkey cell to make proteins for its envelope. b) The virus is a prophage. c) The virus gets an envelope that contains host molecules when it leaves the host cell. d) The virus fools its host by mimicking its proteins. 13) Which of these is classified as an emerging virus that can have a direct impact on human health? (10.19) a) tobacco mosaic virus b) pneumonia c) Ebola d) lambda 14) How do retroviruses such as HIV differ from other viruses? (10.20) a) They can reproduce only inside living cells. b) They contain DNA that is used as a template to make RNA. c) They have much simpler reproductive cycles than other RNA viruses. d) They contain the enzyme reverse transcriptase. 15) Reverse transcription, carried out by retroviruses, is the process by which. (10.20) a) RNA information is copied into DNA b) DNA information is copied into RNA c) RNA information is "read" to form a protein molecule d) DNA is duplicated Answers: 1. B. 2.A, 3. D., 5. B., 6. D., 7. A., 8. A., 9. D., 10. B, 11. C, 12. C, 13. C, 14. D., 15. A