Question

Difference between generalised and specialised transduction

Answer 1

Answer:

difference:-

Explanation:

Key Difference – Generalized vs Specialized Transduction

Transduction is a mechanism which transfers DNA from one bacterium to another bacterium by a bacteriophage. Bacteriophage is a virus that infects and replicates within a bacterium. It is capable of attaching to the bacterial cell wall and injecting its DNA to the bacterium. Inside the bacterium, viral DNA replicates and creates necessary components and enzymes to make new many bacteriophages. During this process, bacterial DNA degrades into pieces and integrates with viral genome or, viral DNA directly integrates with bacterial DNA. New bacteriophages bear the bacterial DNA inside them. When these bacteriophages infect another bacteria, mixing of bacterial DNA occurs. Transduction can happen either by lytic cycle or lysogenic cycle based on the type of the bacteriophage. Hence, there are two types of transduction namely generalized transduction and specialized transduction. The key difference between generalized and specialized transduction is that generalized transduction is done by virulent bacteriophages in which bacterial cell is lysed when new bacteriophages are released while specialized transduction is done by temperate bacteriophages in which bacterial cell is not lysed, and viral DNA integrates with bacterial DNA and survives in prophage stage within the bacteria for several generations.

Answer 2

Explanation:

1. Generalized transduction:

If all the fragments of donor DNA from any region of chromosome have a chance to enter into transducing bacteriophage then it is known as generalized transduction.

In this type of transduction, at first bacteriophage infects donor cell and begins lytic cycle.

When virus enter into bacterial cell, virus hijack host cell and synthesize virus components such as genome, enzymes, capsid, head tail and tail fibers. Then viral enzyme hydrolyses host cell DNA into small fragments.

During assembly of virus component to form progeny viruses, sometime any of the fragments of donor DNA get incorporated into the virus capsid (bacteriophage head). Such abnormal bacteriophage when infects a new cell, it can transfer this donor DNA into new bacteria. Since this donor DNA is not viral DNA, it does not replicates inside recipient bacteria but undergoes homologous recombination with recipient cell’s chromosomal DNA forming recombinant cell.

Figure: generalized transduction

2. Specialized transduction:

In specialized transduction, bacteriophage transfer only a few restricted gene (DNA fragments) from donor bacteria to recipient bacteria. Specialized transduction is carried only by temperate bacteriophage which undergoes lysogenic cycle in donor cell.

At first temperate bacteriophage enter into donor bacteria and then its genome gets integrated with host cell’s DNA at certain location and remains dormant and pass generation to generation into daughter cell during cell division. The bacteriophage which follows lysogenic cycle is known as temperate phage.

When such lysogenic cell is exposed to certain stimulus such as some chemicals or UV lights, it causes induction of virus genome from host cell genome and begins lytic cycle.

On induction from donor DNA, this phage genome sometimes carries a part of bacterial DNA with it. The bacterial DNA lies on sides of integrated phage DNA are only carried during induction.

When such bacteriophage carries a part of donor bacterial DNA infects a new bacteria, it can transfer that donor DNA fragments into new recipient cell. So, in this specialized transduction only those restricted gene are situated on the side of integrated viral genome have a chance to enter into recipient cell.