Question

Describe the three modes that prokaryotes can 'obtain' new genes. Be sure to identify similarities and differences between the three modes. How does the concept of new gene introduction change the view that prokaryotes are asexual species?

Answer 1

The three modes by which bacteria exchange genes with one another are conjugation, transduction and transformation.

Conjugation is the process of transfer of plasmid from one bacterium to the other. The bacteria which contains the plasmid is called as the donor bacterium and the bacteria which is going to receive the plasmid is called as recipient bacterium. It takes place with the help of conjugation tube which is formed between the two bacteria. The donor bacterium makes a copy of the plasmid which is to be transmitted and then transmits it so in the end, we have to bacteria with the plasmid.

Transduction is the process of transfer of viral genes into the bacteria. The virus infects a bacterium and inserts its genome into the bacteria which is there inserted into the bacterial genome. The bacteria that replicates along with the viral genome. The viral genome inside the bacteria capture the bacterial machinery and synthesizers viral particles. This leads to the Assembly of virus inside the bacteria which is released by lysing the bacterial cell.

The third process of genetic exchange in bacteria is transformation. It is the ability of a bacterial cell to pick up DNA from the environment point the bacterial cell which is capable of picking up DNA is called as competent cell. This bacterial cell has pores in its cell wall and plasma membrane by which DNA enters inside the cell.

Similarities between the three types of processes -

All the three processes are means of genetic exchange in bacteria.

Differences between the three processes -

Conjugation involve the transfer of plasmid DNA whereas other two involve the transfer of genomic DNA.

Conjugation requires direct contact between two bacteria whereas other two do not.

Transduction requires a viral vector for the transfer of genes whereas other two do not.

Unlike conjugation and transduction, transformation does not require any vector or external agent for the transfer of genes.

Last part -

The concept of genetic exchange in bacteria has changed the definition of species undergoing asexual reproduction. Earlier it was thought that these prokaryotic cells do not exchange genetic material with other cells and therefore do not show sexual reproduction. But the discovery of these processes in prokaryotes have lead us to understand that although true sexual reproduction is absent but means of exchange of genetic material between two cells is present.

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