Question

Which type of DNA is found in bacteria?

Answer 1

Hint: Bacteria is a unicellular prokaryotic organism. They lack true nucleus and membrane-bound cell organelles. No organelles like the one in eukaryotic cells are present in prokaryotic cells except ribosomes. The ribosomes present in them are of 70S and are associated with the plasma membrane.
DNA is a polynucleotide chain which acts as a genetic material in most organisms.

Complete answer:
Bacteria don’t possess any membrane-bound organelles. As membrane-bound organelles are absent, bacteria don’t have any well-defined nuclei in them. The genetic material or DNA present in them is basically naked and is not enveloped by the nuclear membrane. Though they don’t possess any defined nucleus, the DNA is not scattered throughout the cell. DNA present in them is held in a region known as nucleoid with the help of positively charged proteins. The DNA in nucleoids is organized in long loops held by proteins. The DNA present in bacteria is of two types- Genomic DNA and Plasmids.
Genomic DNA- Most bacteria have a genome that consists of a single DNA molecule that is one chromosome present in them.
Bacterial genomic DNA is several million base pairs in size.
They are circular in shape and don’t have ends like the chromosomes in eukaryotes.
Plasmid- They are small circular DNA present outside the genomic DNA. The plasmid DNA has the capability to replicate autonomously and it can increase its number.
Plasmid DNA confers certain unique phenotypic characteristics to bacteria in which they are present. One such property is resistance to antibiotics.
Plasmid DNA is used to monitor bacterial transformation with foreign DNA.

Note:
Plasmids can replicate within bacterial cells and are independent of the control of chromosomal DNA. Some plasmids may have only one or two copies per cell whereas other bacteria may have 15-100 copies of plasmid per cell. They are used as cloning vectors in biotechnology. When foreign DNA is ligated with the plasmid, we can multiply the foreign gene in hosts equal to the copy number of the plasmid.