Some types of viruses temperature bacteriophages can switch between replication methods cycle a is the blank cycle and cycle B is the blank cycle
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The two cycles are known as the lytic cycle and the lysogenic cycle. Show more…
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The life cycle of a temperate phage involves two main cycles: the lytic cycle and the lysogenic cycle. In the lytic cycle, the temperate phage infects a bacterial cell and takes over the cell's machinery to replicate its own genetic material and produce new phage particles. The first step is the attachment of the phage to specific receptors on the bacterial cell surface. Once attached, the phage injects its genetic material, which can be either DNA or RNA, into the bacterial cell. The phage genetic material then takes control of the cell's machinery and directs it to produce viral components, such as capsid proteins and enzymes necessary for phage replication. Next, the phage genetic material is replicated, and new phage particles are assembled within the bacterial cell. This process involves the synthesis of viral proteins and the packaging of the replicated genetic material into new phage particles. Eventually, the bacterial cell lyses, or bursts open, releasing the newly formed phage particles into the surrounding environment. These phage particles can then go on to infect other bacterial cells and continue the lytic cycle. In the lysogenic cycle, the temperate phage integrates its genetic material into the bacterial chromosome, becoming a prophage. This integration is facilitated by specific proteins produced by the phage. Once integrated, the prophage is replicated along with the bacterial chromosome during cell division, ensuring that the phage genetic material is passed on to daughter cells. During the lysogenic cycle, the prophage remains dormant within the bacterial cell and does not produce new phage particles. The bacterial cell continues to divide and carry out its normal functions, while also harboring the phage genetic material. However, certain environmental cues, such as exposure to UV radiation or certain chemicals, can trigger the prophage to exit the lysogenic cycle and enter the lytic cycle. When the prophage is induced to enter the lytic cycle, it excises itself from the bacterial chromosome and proceeds with the steps described earlier in the lytic cycle. The phage genetic material is replicated, new phage particles are assembled, and the bacterial cell lyses, releasing the phage particles. The ability of temperate phages to switch between the lytic and lysogenic cycles provides them with a survival advantage. The lysogenic cycle allows the phage to persist within the bacterial population without killing the host cells, while the lytic cycle allows for the rapid production and spread of phage particles.
Madhur L.
Phage are viruses that must infect bacteria to reproduce. Viral genomes do not contain all the genes needed to produce all proteins necessary for DNA replication, RNA transcription, and protein translation; instead, the viruses force bacterial proteins and enzymes to express phage genes instead of bacterial genes. Phage are very adaptable, and their behavior depends on whether conditions are favorable or unfavorable for making more phage. When bacteria are plentiful (favorable conditions), viral DNA within the bacteria remains separate from the bacterial chromosome, and the virus forces the bacteria to make more virus. When the amount of virus becomes too much for the cell to hold, the membrane ruptures, and viruses are released to infect surrounding bacteria. This is known as the lytic cycle. When bacteria are scarce (unfavorable conditions), the viral DNA within the bacteria becomes integrated into the bacterial chromosome. The bacteria survive and are still able to reproduce; viral DNA is transmitted to daughter cells when the bacteria reproduces. This is known as the lysogenic cycle. Part A As you just read, phage depend on bacteria to reproduce. Phage can be maintained by infecting a culture of bacteria with a strain of phage, and then plating the bacteria on an agar plate to grow. Suppose that you isolate two mutant strains of phage - one strain cannot enter the lytic cycle and the other strain cannot enter the lysogenic cycle. You also grow wild-type phage as a control. You see three different phenotypes: A plate with no missing bacteria - the lawn of bacteria is intact A plate with spots/circles (called plaques) where there are absolutely no bacteria in the circles A plate with spots/circles (called plaques) where there are some bacteria in the center of the circles. Based on what you know about what happens in each cycle, match the plating results with the identity of the strain. Drag each plate into the correct category.
The Lysogenic Cycle is another type of viral reproductive cycle in which the genome of the phage is replicated without destroying the host. Phages capable of using both modes of reproduction (lytic and lysogenic) are referred to as temperate phages. a) During the lysogenic cycle, the phage genome is mostly silent within the bacteria. Why?
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