Download Lysogenic Cycle

Name: Mrs. Elizabeth Pitchiah
Planned lesson date: 3/13/2014
Subject: Genetics
Grade: 9-12
Lesson Objectives
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2 or 3 student outcomes
Begin with verb
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National/ State
Standards
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AL College & Career
Ready Course of Study
- Common Core
Learning Targets /
District Standards
National Standards
(NCTM; NCTE; etc.,)
Pre-Instructional
activities
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Review
Formative Assessment
Introductory Set
Prior Knowledge
Essential Questions
Problem Question
Writing Prompts
Predictions / Purpose
Vocabulary
Students will be able to describe the differences between RNA and DNA viruses,
and the lytic cycle and lysogenic cycle
(Alabama COS.11)
Describe the replication of DNA and RNA viruses, including lytic and lysogenic
cycles, using diagrams.
1. Review: Review with your students what they know about viruses. Be
sure they understand that viruses occur in plants, as well as animals. (You
might cite the tobacco mosaic virus, which kills tobacco plants.)
2. Formative assessment/Do now: Have you ever missed an important
game due to flu? Ask students what causes the flu. How could we prevent
getting the flu?
3. Introductory set: If students could answer that a virus causes the flu, ask
them what other diseases are caused by viruses? Explain to the students
that they would be learning about viruses, and more specifically about the
replication of DNA and RNA viruses. Show the students the following
youtube clip about influenza:
http://www.youtube.com/watch?v=TVLo2CtB3GA&feature=related.
This would lead into the lesson about viruses.
4. Essential questions: What is a virus?
How does virus reproduce?
How does virus infect humans?
5. Vocabulary:
Virus: a disease causing, non-living particle made of proteins, nucleic
acids and sometimes lipids; inside living cells called host cells.
Capsid: Outercoat of protein that surrounds a virus's inner core of nucleic
acid; arrangement of capsid proteins gives a virus its shape.
Bacteriphage: viruses that infect bacteria, also called phages.
Prophage: when the DNA temperate phage is integrated into the host's
chromosome
Lysogenic cycles: viral replication cycle in which a virus's nucleic acid is
integrated into a host cell's chromosome; a provirus is formed and
replicated each time the host cell reproduces; the host cell is not killed
until the lytic cycle is activated.
Lytic cycle: viral replication cycle in which a virus takes over a host cell's
genetic material and uses the host cell's structures and energy to replicate
until the host cell bursts, killing it.
Provirus: viral DNA that is integrated into a host cell's chromosome and
replicated each time the host cell replicates.
Retrovirus: RNA virus that contains reverse transcriptase.
Teaching
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Direct Teaching
Graphic Organizers
Reading Instruction
Tech Integration
Teacher Demonstration
Guided Practice
Independent Practice
Small Group Activities
Experiential Activities
Research / Study
Simulations
Problem Solving
Activities
Differentiated
Instruction
Accommodations
Ongoing Assessment
Direct teaching:
(Give students the vocabulary worksheet)
1. Use Prezi to explain that viruses are classified as a non-cellular particle
made up of protein-covered genetic material that can invade living cells.
Then explain the discovery of viruses.
2. Demonstrate how to make a model of virus. Provide the material needed
for a virus model. Place students in pairs and guide them to make a model
of virus.
3. What is a virus? (Give the work sheet to label parts of virus)
4. Describe the different parts of a virus by labeling a diagram.
5. Explain that virus reproduction requires a cell, and that there are two types
of reproduction cycles: lytic and lysogenic.
6. Show the animation for lytic cycle- Explain
7. Differentiated instruction: Ask students
a. What is the first step in lytic cycle?
b. What happens after virus gets into cell?
c. What happens after many copies of virus have been made?
8. Show the animation for lysogenic cycle- Explain
9. Independent practice: Independently students could compare and
contrast lytic and lysogenic cycles.
10. Show the youtube video that summarizes the lytic and lysogenic cycles.
Closure
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Summary / Conclusions
Re-teaching
Formative Assessment
Review
Reflection
1. Whole class: Review “What is virus?”
2. State 3 things that you learned from the lesson- Collect an exit slip
Key questions:
What is a virus?
How does virus infect humans?
Vocabulary
Virus: a disease causing, non-living particle made of proteins, nucleic acids and
sometimes lipids; inside living cells called host
cells.
Capsid: Outercoat of protein that surrounds a virus's inner core of nucleic acid;
arrangement of capsid proteins gives a virus its shape.
Bacteriphage: viruses that infect bacteria, also called phages.
Prophage: when the DNA temperate phage is integrated into the host's chromosome
Lysogenic cycles: viral replication cycle in which a virus's nucleic acid is integrated into
a host cell's chromosome; a provirus is formed and replicated each time the host cell
reproduces; the host cell is not killed until the lytic cycle is activated.
Lytic cycle: viral replication cycle in which a virus takes over a host cell's genetic
material and uses the host cell's structures and energy to replicate until the host cell
bursts, killing it.
Provirus: viral DNA that is integrated into a host cell's chromosome and replicated each
time the host cell replicates.
Retrovirus: RNA virus that contains reverse transcriptase.
Enveloped with helical nucleocapsid (influenza virus)
How a Virus Infects You
Viruses lie around our environment all of the time just waiting for a host cell to come along.
They can enter us through the nose, mouth or breaks in the skin. Once inside, they find a host
cell to infect. For example, cold and flu viruses will attack cells that line the respiratory or
digestive tracts. The human immunodeficiency virus (HIV), which causes AIDS, attacks the Tcells of the immune system.
Regardless of the type of host cell, all viruses follow the same basic steps in what is known as
the lytic cycle http://sites.fas.harvard.edu/~biotext/animations/lyticcycle.html
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A virus particle attaches to a host cell.
The particle releases its genetic instructions into the host cell.
The injected genetic material recruits the host cell's enzymes.
The enzymes make parts for more new virus particles.
The new particles assemble the parts into new viruses.
The new particles break free from the host cell.
All viruses have some type of protein on the outside coat or envelope that "feels" or "recognizes"
the proper host cell(s). This protein attaches the virus to the membrane of the host cell. Some
enveloped viruses can dissolve right through the cell membrane of the host because both the
virus envelope and the cell membrane are made of lipids.
Those viruses that do not enter the cell must inject their contents (genetic instructions, enzymes)
into the host cell. Those viruses that dissolve into a cell simply release their contents once inside
the host. In either case, the results are the same.
Lysogenic Cycle
Once inside the host cell, some viruses, such as herpes and HIV, do not reproduce right away.
Instead, they mix their genetic instructions into the host cell's genetic instructions. When the host
cell reproduces, the viral genetic instructions get copied into the host cell's offspring.
The host cells may undergo many rounds of reproduction, and then some environmental or
predetermined genetic signal will stir the "sleeping" viral instructions. The viral genetic
instructions will then take over the host's machinery and make new viruses as described above.
This cycle, called the lysogenic cycle, is shown in the accompanying figure.
Because a virus is merely a set of genetic instructions surrounded by a protein coat, and because
it does not carry out any biochemical reactions of its own, viruses can live for years or longer
outside a host cell. Some viruses can "sleep" inside the genetic instructions of the host cells for
years before reproducing. For example, a person infected with HIV can live without showing
symptoms of AIDS for years, but he or she can still spread the virus to others.
In the lytic cycle, the bacterial cell wall is ruptured and the progeny phages are released. Thus the host is
destroyed.
In the lysogenic cycle, the host remains intact and through excision the progeny is released.
Both are the cycles describing the proliferation of bacteriophages in a host bacterial cell.
lytic:
shorter, immediate symptoms, does not take over dna of cell
lysogenic:
longer, can remain dormant for years, prolonged symptoms, takes over or bcomes part of cells dna
similarities:
both produce viruses in the end
contrast
In lytic cycle, the virus is virulent i.e. infectious.
In lysogenic life cycle, the virus may remain non infectious due the suppressor enzyme which acts on
itself. if this enzyme is somehowq destryoed the virus enters virulent stage again & undergo lytic cycle
Objectives
Students will understand the following:
1. A virus is an infectious organism that reproduces within the cells of an infected host.
2. A virus is not alive until it enters the cells of a living plant or animal.
3. A virus contains genetic information wrapped in a protein coat.
4. Viruses can be useful as well as harmful.
5. A virus that mutates ensures its own survival by making itself unrecognizable to immune systems and vaccines.
6. Even viruses engineered for useful purposes can be harmful if unchecked.
http://www.discoveryeducation.com/teachers/free-lesson-plans/understanding-viruses.cfm
http://www.ck12.org/biology/DNA-Structure-and-Replication/
http://education-portal.com/academy/lesson/viruses-bacteriophage-lytic-and-lysogeniccycles.html#lesson