A virus can only make copies of itself inside a ..., dead cell, nutrient agar plate, living host cell, drop of clean water, A virus that infects bacteria is called a ..., prion, viroid, protozoan, bacteriophage, What is the FIRST step of a virus replication cycle?, Assembly of new virus particles, Attachment (adsorption) to the host cell, Release from the host cell, Synthesis of viral proteins, The lytic cycle ends when ..., the host cell bursts and releases new viruses, the viral DNA joins the host chromosome, the host cell divides normally, the virus becomes inactive for many years, In the lysogenic cycle, the phage DNA is inserted into the ..., bacterial chromosome, bacterial cell wall, bacterial ribosome, phage capsid, Phage DNA that is integrated into a bacterial chromosome is called a ..., capsomere, virion, plasmid, prophage, A phage that can follow either the lytic cycle or the lysogenic cycle is called a ..., virulent phage, defective virus, temperate phage, satellite virus, A phage that can ONLY follow the lytic cycle is called a ..., temperate phage, virulent phage, prophage, latent phage, The protein coat that surrounds the genetic material of a virus is the ..., capsid, envelope, cell wall, nucleus, Which part of bacteriophage T4 recognises and binds to receptors on the bacterial cell?, Head (capsid), Tail fibres, Collar, DNA, A complete, infectious virus particle outside a host cell is called a ..., prophage, provirus, virion, capsomere, During penetration, bacteriophage T4 ..., enters the cell whole by endocytosis, fuses its envelope with the cell membrane, dissolves the whole bacterial cell wall, injects its DNA into the cell while the capsid stays outside, In the biosynthesis stage, ..., the virus attaches to the cell surface, new viruses leave the cell, the host cell makes antibodies against the virus, the host cell's machinery makes viral nucleic acids and proteins, In the assembly (maturation) stage, ..., the viral genome is injected, the cell divides into two cells, new viral parts are put together to form new virions, the viral DNA is cut out of the chromosome, Budding is a way of release in which the virus ..., pushes out through the host cell membrane and takes part of it as an envelope, breaks the cell wall with enzymes, is released only when the cell dies, passes through gap junctions to the next cell, Viruses that leave the host cell by budding usually have ..., a tail and tail fibres, an envelope, a cell wall, no genetic material, Release by exocytosis means that new viruses ..., burst out of the cell all at once, are digested by lysosomes, are carried in vesicles that fuse with the plasma membrane, stay inside the nucleus, The envelope of a virus released by budding comes from the ..., viral capsid, host cell wall, host ribosomes, host cell membrane, Which virus is released mainly by budding?, Bacteriophage T4, Influenza virus, Poliovirus, Tobacco mosaic virus, In the lysogenic cycle, the prophage is copied when ..., the host bacterium divides, the host cell bursts, the phage attaches to a new cell, the phage capsid is assembled, The switch of a prophage from the lysogenic cycle to the lytic cycle is called ..., integration, adsorption, induction, transcription, Which factor can trigger a prophage to enter the lytic cycle?, Plenty of nutrients, Ultraviolet (UV) light, Normal temperature, Low light, An acute viral infection is one that ..., starts quickly, lasts a short time, and is then cleared by the immune system, lasts for the whole life of the host, never causes symptoms, only infects plants, A persistent viral infection is one in which ..., the virus is cleared within a few days, the virus cannot enter cells, the host cell always bursts quickly, the virus stays in the body for months or years, Shingles (herpes zoster) is caused by the reactivation of a latent ..., influenza virus, poliovirus, rabies virus, varicella-zoster virus, Which disease is a typical example of a CHRONIC viral infection?, Common cold, Hepatitis B, Influenza, Chickenpox, HIV uses which enzyme to make DNA from its RNA genome?, Reverse transcriptase, DNA ligase, Protease, Amylase, HIV DNA that is integrated into the DNA of a human cell is called a ..., prophage, capsid, provirus, virion, HIV mainly infects which human cells?, CD4 helper T cells, Red blood cells, Skin cells, Bone cells, The number of new phages released from ONE infected bacterium is called the ..., latent period, plaque, multiplicity of infection, burst size, What is the correct order of the stages in the lytic cycle?, Penetration → attachment → assembly → biosynthesis → release, Attachment → penetration → biosynthesis → assembly → release, Attachment → biosynthesis → penetration → release → assembly, Attachment → integration → cell division → induction → release, What is the MAIN difference between the lytic and the lysogenic cycle?, In the lysogenic cycle the viral genome is integrated and the host survives and divides; in the lytic cycle the host is destroyed quickly, Only the lytic cycle needs attachment to a host cell, Only the lysogenic cycle produces viral proteins immediately, The lytic cycle only occurs in animal cells, Most viruses can infect only certain species or cell types. This is mainly because ..., viruses are too large to enter most cells, all host cells have the same receptors, viral attachment proteins must fit specific receptors on the host cell surface, viruses can only use the ribosomes of bacteria, The 'eclipse period' of a viral infection is the time when ..., the virus is attached but has not entered the cell, the cell bursts and releases many virions, the immune system destroys all viruses, no complete infectious virions can be found inside the infected cell, Animal viruses usually need an 'uncoating' step, but bacteriophage T4 does not. Why?, T4 has no capsid, Bacteria have no cytoplasm, Animal viruses are smaller than phages, T4 injects only its DNA, so its capsid never enters the cell, How do most animal viruses enter their host cells?, By injecting DNA through a tail, By receptor-mediated endocytosis or by fusion of the envelope with the cell membrane, By drilling through the cell wall, By passive diffusion through membrane pores, Corynebacterium diphtheriae produces diphtheria toxin only when it carries a certain prophage. This is an example of ..., lysogenic conversion, generalised transduction, lytic infection, abortive infection, In a one-step growth curve of a phage, the sudden rise in the number of free phages is caused by ..., attachment of phages to new cells, integration of the phage genome, lysis of the infected cells, releasing new virions, uncoating of the phages, Which statement CORRECTLY compares chronic and latent infections?, In latent infection virus is made continuously; in chronic infection no virus is made, Both are cleared within one week, Chronic infections occur only in bacteria and latent infections only in plants, In chronic infection new virus is made continuously; in latent infection the genome is present but virus is not made until reactivation, Why does release by budding help a virus cause a persistent infection?, The host cell can survive and keep producing viruses for a long time, Budding destroys the cell faster than lysis, Budding viruses have no proteins for antibodies to recognise, Budding removes the virus genome from the cell, Hepatitis B virus gets its envelope from internal membranes and leaves the cell in vesicles. This type of release is ..., lysis, exocytosis through the secretory pathway, binary fission, budding through the cell wall, The influenza enzyme neuraminidase is important during release because it ..., copies the viral RNA in the nucleus, injects the genome into the cell, cuts sialic acid so new virions can detach from the cell surface, joins viral DNA to host DNA, After a cold sore heals, herpes simplex virus type 1 stays latent mainly in ..., red blood cells, the stomach lining, skeletal muscle fibres, sensory nerve ganglia (neurons), A bacterium that already carries a lambda prophage cannot be infected again by another lambda phage. This is called ..., lysogenic conversion, immunity to superinfection, induction, transduction, A retrovirus such as HIV and a temperate phage such as lambda are similar because both ..., can insert their genome into the host cell's DNA, have RNA genomes, always kill the host immediately, infect only human cells, When a phage carries bacterial DNA from one bacterium to another, the process is called ..., transformation, conjugation, transduction, translation, Why are enveloped viruses such as influenza and coronaviruses easily destroyed by soap or alcohol?, Soap and alcohol break down their lipid envelope, which they need to attach to cells, Soap digests their DNA, Alcohol makes the capsid stronger, Soap blocks their reverse transcriptase, A patient on HIV therapy (ART) has undetectable virus, but the virus returns quickly after the therapy stops. The best explanation is that ..., HIV becomes a bacteriophage, ART kills all CD4 cells, the virus is made again from the patient's own genes without infection, proviruses remain latent in resting cells, where ART cannot reach them, In virology, the term 'virulence' means ..., the number of genes a virus has, how severe a disease a virus can cause, the size of the viral capsid, the speed at which a virus mutates, A virus enters a cell but cannot complete its replication cycle, so no new virions are produced. This is called ..., a productive infection, a lytic infection, an abortive infection, a chronic infection, E. coli cells that carry the lambda prophage are exposed to UV light. About an hour later many cells lyse. Which sequence best explains this?, UV kills the bacteria directly → phages then enter the dead cells, UV makes the bacteria produce new receptors → more phages attach, UV causes new phages to be assembled from the cell membrane, UV damages DNA → the SOS response activates RecA → the lambda repressor is cleaved → the prophage is excised and enters the lytic cycle, A student spreads a phage on a lawn of bacteria. One phage produces clear plaques, another produces turbid (cloudy) plaques. The turbid plaques most likely come from a ..., virulent phage, because it kills every cell in the plaque, phage that cannot attach to the bacteria, temperate phage, because some infected cells become lysogens that are immune and keep growing inside the plaque, phage that has lost its capsid, In an experiment, 2 × 10^6 bacteria are each infected by one phage. After one cycle, 3 × 10^8 new phages are released. What is the average burst size?, 15, 150, 600, 1,500, Oseltamivir blocks influenza neuraminidase. Which outcome is MOST expected in a cell that is already infected?, New virions are still made but stay attached to the cell surface, so spread to other cells is reduced, The virus can no longer enter the nucleus, The viral RNA can no longer be copied, The host cell immediately bursts, Scientists make an HIV mutant with a non-working integrase. What is the most likely result?, The virus cannot attach to CD4, The virus cannot make DNA from RNA, The virus can no longer bud from the cell, The viral DNA cannot join the host genome, so a stable provirus and a latent reservoir cannot form, Virus X kills its host cell after 8 hours and releases 1,000 virions. Virus Y buds slowly, releasing about 10 virions per hour for many weeks while the cell stays alive. Which statement is best supported?, Virus X is more likely to be persistent because it makes more virions per cell, Both viruses must be latent viruses, Virus Y is more likely to cause a persistent infection because infected cells survive and keep producing virus with less tissue damage, Virus Y cannot be enveloped because it does not kill the cell, Drugs for chronic hepatitis B block reverse transcription of pregenomic RNA, but they rarely cure the infection. Why?, Hepatitis B virus has no DNA, They do not remove the cccDNA that stays in the nucleus and keeps producing viral RNA, The drugs destroy the liver cells, Hepatitis B virus is released only by lysis, Phage lambda integrates next to the gal genes of E. coli. Lambda phages produced after induction can transfer the gal genes, but almost never other bacterial genes. This is ..., specialised transduction, caused by imprecise excision of the prophage, generalised transduction, caused by random packaging of host DNA, transformation, caused by uptake of free DNA, conjugation through a pilus, Put these budding events of an enveloped virus in the correct order: (1) the membrane wraps around the nucleocapsid; (2) viral glycoproteins move from the Golgi to the plasma membrane; (3) the bud pinches off; (4) matrix proteins and the nucleocapsid gather under the modified membrane., 2 → 4 → 1 → 3, 4 → 2 → 3 → 1, 1 → 2 → 4 → 3, 2 → 1 → 3 → 4, A 70-year-old man who had chickenpox as a child develops a painful rash in a band on only one side of his chest. Which explanation is best?, He was newly infected with chickenpox from a child, Weaker cell-mediated immunity with age lets latent varicella-zoster virus reactivate in one sensory ganglion and travel along that nerve to the skin, The virus was in his skin cells since childhood and multiplied slowly, Bacteria in the skin turned into varicella-zoster virus

Virus Replication

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