Question

27. Which of the following is not a mode of action of antivirals? A) block penetration; B) block transcription and translation; C) inhibit DNA synthesis; D) block maturation; E) bind to ergosterol 28. Lysogeny is A) an infection by alytic phage; B) a condition when a viral genome is integrated into the host chromosome but does not result in the lysis of the host cell; C) when the infecting phage exists as a prophage; D) caused by a temperate phage; E) all except A 29. In nature, antibiotics are known to be produced from all the following except: A) Penicillium; B) Bacillus, C) E coli, D) Streptomyces, E) Cephalosporium 30. Surfactants work by:

all please

Answer 1

27.(D) Not Action of antivirals is Block maturation

28 (E) Two method of viral replication

1.Lytic :To start with, the virus has to infect the cell. So the virus attaches itself to the outer cell wall and releases enzymes that weaken the cell wall. Then, depending on whether it is a DNA virus or a RNA virus, the virus injects its double stranded DNA or its single stranded RNA into the cell.

The Lytic Cycle

In the lytic cycle, which is considered the main cycle in viral replication, once the viral DNA enters the cell it transcribes itself into the host cell's messenger RNAs and uses them to direct the ribosomes. The host cell's DNA is destroyed and the virus takes over the cell's metabolic activities.

The virus begins using the cell energy for its own propagation. The virus produces progeny phages. These replicate fast, and soon the cell is filled with 100-200 new viruses and liquid. As the cell starts getting overcrowded, the original virus releases enzymes to break the cell wall. The cell wall bursts – this process is called lysing - and the new viruses are released.

So, in short, in the lytic cycle, the virus hijacks the infected cell and then destroys it. The lytic cycle occurs in virulent viruses. The symptoms from a viral infection occur when the virus is in a lytic state.

The Lysogenic Cycle

In the lysogenic cycle, the viral DNA or RNA enters the cell and integrates into the host DNA as a new set of genes called prophage. That is, the viral DNA becomes part of the cell's genetic material. No progeny particles, like in the lytic phase, are produced. Each time the host cell DNA chromosome replicates during cell division, the passive and non-virulent prophage replicates too. This may alter the cell's characteristics, but it does not destroy it.

There are no viral symptoms in the lysogenic cycle; it occurs after the viral infection is over. But the viral DNA or RNA remains in the cell and it may remain there permanently. However, if the prophage undergoes any stress or mutation or is exposed to UV radiation, the viral lysogenic cycle can change into the viral lytic cycle. In which case, there will be symptoms of a new viral infection.

29.(C)

Penicillium -penicillins are derived from 6-Amino-penicillanic acid

Cephalosporium all the drugs in this group contain a Beta-lactam ring in their structure.

Streptomyces -Streptomycin drug ued of treatment tularemia,Brucellosis

30.(D) distrupting membrane integrity

Bacillus-bacillus perfringens,Bacillus diphtheriae procuces antibodies

The