Presentation1 mcb.ppt
- 2. Plasmids are known to be small, circular molecules of DNA that have the ability to replicate independently, as they do not depend on the organism’s chromosomal DNA for replication. Due to this, plasmids are also known as extrachromosomal DNA. Plasmids are vital tools in genetic engineering as they help in gene cloning and gene therapy. EXTRA CHROMOSOMAL DNA (PLASMIDS)
- 4. Who Discovered Plasmids? The word Plasmid was first coined by Joshua Lederberg in 1952. The term was first described in a research paper he published describing the experiments carried out by himself and his student Norton Zinder. The experiment was conducted on salmonella bacteria and its virus P22.
- 5. OCCURRENCE OF PLASMIDS Plasmids are found in bacterial cells and certain eukaryotes. A plasmid measures up to 1 to 200 kb in size and produces enzymes that can degrade antibiotics or heavy metals
- 7. •Helps in their survival by producing toxins. •Facilitate the process of replication in bacteria. •Few plasmids contain genes that help in food digestion. •The R plasmids help a bacterial cell by defending against environmental factors such as antibiotics, poison, etc. IMPORTANT FUNCTIONS OF PLASMID IN BACTERIA
- 8. Characteristics - Plasmids i. Plasmids almost always carry at least one gene ii. Plasmids can also provide bacteria with the ability to fix nitrogen. iii. Plasmids may be present in an individual cell in varying number, ranging from one to several hundreds. iv. Larger plasmids tend to have lower copy numbers. v. There are some plasmids in which no effect is observed on the host phenotype. Such types are called cryptic plasmids
- 9. Plasmid – Functions Plasmids have various functions and the list is given below. 1.They carry at least 1 gene, and most of the genes are helpful to their host organisms. 2.They increase the survival of the organism 3.Facilitate the process of replication.
- 10. Why is Plasmid Important? They are important for the role they play in technological breakthroughs. 1.They have played a stellar role in the development of molecular biotechnology. 2.They act as vehicles to introduce foreign DNA into bacteria. 3.The DNA they deliver have genes for antibiotic resistance. 4.It is a therapeutic platform for treating infectious, genetic and acquired diseases.
- 11. Types of Plasmids Five types of plasmids are given below. 1.Resistance Plasmids 2.Virulence Plasmids 3.Degradative Plasmids 4.Col Plasmids 5.Fertility F Plasmids
- 12. •Fertility F-plasmids, which contain tra genes. They are capable of conjugation and result in the expression of sex pilli. •Resistance plasmids, which contain genes that provide resistance against antibiotics or poisons. They were historically known as R-factors, before the nature of plasmids was understood. •Col plasmids, which contain genes that code for bacteriocins, proteins that can kill other bacteria. •Degradative plasmids, which enable the digestion of unusual substances, e.g. toluene and salicylic acid. •Virulence plasmids, which turn the bacterium into a pathogen.
- 13. Conjugative plasmids contain tra genes, which perform the complex process of conjugation, the transfer of plasmids to another bacterium. Non-conjugative plasmids are incapable of initiating conjugation, hence they can be transferred only with the assistance of conjugative plasmids. An intermediate class of plasmids are mobilizable, and carry only a subset of the genes required for transfer. They can parasitize a conjugative plasmid, transferring at high frequency only in its presence.
- 14. It is possible for plasmids of different types to coexist in a single cell. Several different plasmids have been found in E. coli. However, related plasmids are often incompatible, in the sense that only one of them survives in the cell line, due to the regulation of vital plasmid functions. Thus, plasmids can be assigned into incompatibility groups. INCOMPATIBILITY