Identify the function of plasmid DNA.

The correct answer is To confer certain unique phenotypic characteristics to bacteria.

Key Points

• Plasmid
  • The plasmid is an extrachromosomal genetic element used in genetic engineering that occurs in many bacterial strains.
  • Plasmids are circular deoxyribonucleic acid (DNA) molecules that replicate independently of the bacterial chromosome.
  • They are not essential for the bacterium but may confer a selective advantage.
  • One class of plasmids, carcinogenic (or Col ) factors, determines the production of proteins called colicins, which have antibiotic activity and can kill other bacteria.
  • Another class of plasmids, R factors, confers upon bacteria resistance to antibiotics.
  • Some Col factors and R factors can transfer themselves from one cell to another and thus are capable of spreading rapidly through a bacterial population.
  • A plasmid that is attached to the cell membrane or integrated into the bacterial chromosome is called an episome.

Additional Information

• DNA molecule is packaged into thread-like structures called chromosomes.
• They are present in the nucleus of each cell.
• Each chromosome is made up of DNA tightly coiled around many times around proteins called histones that support its structure.
• Chromosomes are made up of a DNA and protein complex found in the nucleus of eukaryotic cells.
• It is made of proteins and a single molecule of deoxyribonucleic acid (DNA).
• The DNA and proteins together form chromatin fibres, which gets further condensed into chromosomes.
• This condensation or packaging of the DNA helps to accommodate long DNA molecules inside the nucleolus.