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Definition
| Has a genome but can reproduce only within a host cell. their reproduction usually leads to weakening of the host cell and causes viral diseases suffered by plants and animals. |
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Term
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Definition
| representatives of prokaryotes are remarkable in their ability to reproduce rapidly and utilize a vast array of substance as sources of energy and nutrients. |
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Term
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Definition
Viroids are ciruclar RNA molecules of only several hundred nucleotides.
Prions are misfolded form of protiens that appears to cuase normal protiens to also misfold.
Both viroids and Prions and the simplest known agents to cause diseases. |
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Term
| What does viruses contain and how big are they? |
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Definition
| Viruses are much smaller than the smallest bacterium and typically consist of just a nucleic acid and a few protiens. |
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Term
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Definition
| Viruses enter the cells and use the host cell capabilities for DNA replication and protein synthesis to reproduce themselves. |
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Term
| What happens when the host cells releases new viruses? What are virions? |
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Definition
When a host cell releases new viruses, it usually means that the host cell is dead.
individual virus particles outside the host cell. |
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Term
| What does a virion consist of? |
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Definition
| It consist of a center core of either DNA or RNA surrounded by a protein capsid, and sometimes a membrane envelope. |
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Term
| What are Bacteriophages or phages? |
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Definition
| are viruses that infect and kill bacteria |
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Term
What is a lytic cycle?
how does it work? |
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Definition
A phages reproductive cycle leading to the death of a bacteria.
Phages will attach to the surface of a bacteria and inject its DNA in to the cell, then it reproduces inside the cell and finally the host cell dies and burst releasing all of the new made phages. |
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Term
| What is a lysogenic cycle? |
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Definition
Lysogenic cycle doesnt kill the host cell.
The phages DNA is not immediately used to produce more phages, rather it is incorporated into the circular chromosome of the bacteria cell. When incorporated together the phage DNA is known as a prophage
the cell divides and replicates with the phages DNA passing it on to the daughter cells.
Eventually, the viral DNA in the prophage form is activated and switches to the lytic cycle where it releases the phages from a large number of bacteria cells containing prophages. |
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Term
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Definition
| they shut down the host cell transcription while the viral genome is replicated. |
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Term
How does phage genes work to shut down cell transcription and replicate viral genome?
WEhat are early genes and late genes? |
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Definition
*the viral genome contains a promoter that attracts the cell RNA polymerase which transcribes the viral genes.
*EArly genes code proteins that shut down transcription of the host cell while stimulating viral genome replication. One of the proteins actually digest the host cell DNA to provide nucleotides for synthesis of viral DNA.
*LAte genes codes for proteins of the viral capsid and proteins that lead to lysis of the becteria cell to release the virions. |
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Term
| Genome of animal viruses can be... |
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Definition
| single o double stranded RNA or DNA, and commonly surrounded by a membrane envelope. |
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Term
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Definition
| Virus that causes respiratory flu is an RNA virus enclosed in a membrane envelope derived from the host cell. |
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Term
| How does the influenza virus work? |
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Definition
*it is taken into the cell by endocytosis
*once inside the cell, the virus is released from the vesicle.
*Single strand RNA genome is replicated, and the assembled virions exit the cell by a budding process.
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Term
| What does the envelope of the host cell consist of? |
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Definition
| plasma membrane and glycoproteins made in the ER from a viral gene. |
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Term
| What happens when the host cell is infected with the influenza virus? |
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Definition
| It weakens the host cell and contributes to the symptoms associated with the repiratory flu. |
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Term
| How do u recover from viruses? |
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Definition
| Viruses are not affected by anti bodies, so it depends on your immune system to recognize the virus and kill it. |
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Term
| What is the human immunodeficiency virus? (HIV) |
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Definition
| enveloped RNA virus that uses reverse transcriptase to produce a DNA provirus. |
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Term
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Definition
| Retrovirus are RNA virus that contains an enzyme (reverse transciptase) which transcribe an RNA template into DNA. |
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Term
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Definition
*HIV( the retro virus that causes aids) enter the cells of the human immune system and releases reverse transcriptase to convert its RNA genome to DNA.
*The viral DNA is integrated into the host cell chromosome as a provirus, where it remains a permanent resident.
*The host cell RNA polymerase trascribes the proviral DNA to produce the new viral particles that are released from the cell. |
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Term
| What does rapid reproduction, mutation, and genetic recombination contribute to bacterias? |
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Definition
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Term
| How fast can a population of E. coli bacteria double in size? |
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Definition
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Term
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Definition
| Bacterias reproduce asexually by binary fission leading to two genetically identical cells. So a single bacterium can rapidly give rise to a CLONE of genetically i dentical cells. |
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Term
| What are the three ways a bacteria can recombine their genes to cause genetic variation. |
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Definition
| Transformation, Transduction, and Conjugation |
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Term
| What is Transformation and how does it work? |
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Definition
Transformation refers to the alteration of a bacterial cells' genotype and phenotype by the uptake of naked DNA from its surrounding environment (e.g. another cell that has been broken.
Basically introducing foreign genes into a bacteria. |
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Term
| What is transduction and how does it work? |
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Definition
| Transduction is when a phage carries a foreign gene into a bacterial cell as a result of the accidental packaging of a DNA fragment from a phage infected hostcell into the virions. Such a virus is defective becaus it lacks some of its genes needed to reproduce. The defective virion can still inject its DNA into the bacterial cell, resulting in a DNA fragment from the first cell being incorporatd into the genome of the second cell. |
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Term
| What is conjugation and how does it work? |
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Definition
*Conjugation is the direct transfer of genetic material between two baterial cells temporarily joined by a cytoplasmic mating bridge.
*DNA transfer is in one direction. The donor cell attaches a sex pillus to draw the recipient cell close enough to make a conjugation tube between the two cells. Transfer of DNA is a form of plasmids.
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Term
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Definition
| Plasmids are small circular, self-replicating DNA molecule that is separated from the main bacterial chromosome. Plasmids have small number of genes that are not needed for normal growth, but confer advantages on bacteria living in stressful environments. |
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Term
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Definition
| F factors are special pieces of DNA that exist within the bacterial chromosomes. They give the becteria the ability to from sex pilli. |
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Term
| What are transposon genetic elements? |
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Definition
| Transopson also known as "jumping genes" are capable of moving from one location to another on the chromosome by the methods of "copy and paste" or "cut and paste" |
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Term
| What does Transopson contain? |
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Definition
Transposable elements contain a gene that makes a transposase enzyme which catalyze movemoents. Transposon also contains one or more genes along with the transposase enzyme.
So they can insert in the middle of a gene, disrupting its function or creating potentially useful genetic variation. |
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Term
What is an operon and how does it work?
When lactose is present/not present? on E. COli |
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Definition
Operon is the promoter, operator and the three genes they control.
Three genes that uptake and utilize lactose are z,y and a. The order goes promoter, operator, and the three genes on the chromosome. The operator has the ability to switch off all the 3 genes and blocking the RNA polymerase from transcribing it.
When lactose is present, enzymes bind to the lac repressor protien, allowing the RNA polyerase to transcribe.
When lactose is absent, the lac repressor sits on the operator and blocking the RNA polymerase from transcribing.
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Term
| What re Tryotophan (trp) operon? |
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Definition
In the absents of trp, transcription will happen.
If trp is present then it stops transcription from happening and E. COli cells can save energy by turning off trascription of genes for trp synthesis.
Trytophan binds to a repressor protein and changes its confirmation allowing it to bind to the operator and prevent transcription from occuring. This is a Repressible operon. |
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Term
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Definition
| control anabolic pathways, which remain turned on until the product becomes available in the environment. |
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Term
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Definition
| control catabolic pathways which are turned on only when the substrate is available in the environment. |
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