Answer :
Option d.) the bacterium can import free dna fragments from the environment is that the correct answer.
Competent cells are bacterial cells which will accept extra-chromosomal DNA or plasmids from the environment. The generation of competent cells may occur by two methods: natural competence and artificial competence.Natural competence is that the genetic ability of a bacterium to receive environmental DNA under natural or in vitro conditions. Bacteria also can be made competent artificially by chemical treatment and heat shock to make them transiently permeable to DNA. Natural competence dates back to 1928 when Frederick Griffith discovered that prepared heat cells of a pathogenic bacterium could transform the non pathogenic cells into pathogenic type.
In some genera, certain portions of the population are competent at a time, and in others, the full population gains competence at the same time. When the foreign DNA enters inside the cells, it's going to be degraded by the cellular nucleases or may recombine with the cellular chromosome. Artificial competence isn't coded by the genes of the bacterial cells. It's a laboratory procedure in which cells are passively made permeable to DNA using unnatural conditions. The procedure of artificial competence is comparatively simple and easy and can be used to engineer a bacterium genetically. However, transformation efficiency is extremely low as only a portion of the cells become competent to successfully take up DNA.
However, natural competence and transformation are efficient for linear molecules like chromosomal DNA but not for circular plasmid molecules.
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