Question

____ are self-replicating, extrachromosomal segments of double-stranded circular and naked DNA, present in a bacterial cell.
A. Plasmids
B. Nucleoid
C. Mesosomes
D. Bacteriophage

Answer 1

Hint: Plasmids are known as replicons. These naturally exist in bacterial cells and also occur in eukaryotes. The genes carried by the plasmid in the bacteria provide genetic advantages, such as antibiotic resistance. Sometimes plasmids are linear with RNA as the genetic material.

Complete answer:
> Plasmids have a great role in the development of molecular biotechnology. They play the role of delivery vehicles, or vectors, to introduce foreign genetic material into the bacteria. A Plasmid is a small extrachromosomal DNA molecule within the cell that is physically separated from chromosomal DNA and can replicate independently. It is a small, circular, double-stranded DNA molecule that is distinct from a cell’s chromosome DNA. In the laboratory, plasmids can be introduced into the cell via transformation. The length of the plasmid varies normally from one thousand DNA base pairs to hundreds of thousands of base pairs. The plasmids present in the bacterial cell will be distributed in every daughter cell equally during the cell division. Plasmids play an important role in the bacterial evolutionary adaptation which allows them to survive in the changing environment as they are carrying beneficial genes. Plasmids can contain three types of genes: antibiotic resistance genes, transgenes, and reporter genes. These types of plasmid genes may occur naturally or to be engineered by scientists.
There are mainly five types of plasmids found. These are fertility F- plasmids, resistance plasmids, virulence plasmid, degradative plasmids, and Col plasmids.
> F-plasmids comprise tra genes that can conjugate, which result in the expression of sex pilli.
> Resistance plasmids comprise genes that are responsible for providing resistance to the bacteria against poisons or antibiotics.
> Col plasmids comprise genes that can code a protein called bacteriocins, which is capable of killing other bacteria.

Note:
The plasmid is introduced into the bacteria through a process called transformation, and bacteria carrying the plasmid are selected using antibiotics. The plasmid consists of genes which encode plasmid specific replication initiation protein, iterons, AT-rich regions, Dna boxes.