Date: 31. October 2017
Genetics: An Introduction
In this section, the educator discusses the Bacterial Genome, Mutations and Types and Causes of Mutations. Bacterial Genome is a single circular DNA, which comprises of 5000 kbp codes 2000 protein. Plasmid carry very important genes necessary for survival of bacteria such as antibiotic gene resistant.
Mutation is Change in the base sequence of DNA that results in altered protein phenotype. Mutation is of two types; Substitution mutation and Frame shift mutation. Frame shift mutation are the mutations that arise when there is insertion and deletion of 1 or more than one base pairs. It alters the phenotype of protein. Causes of Mutation are Chemical, Radiation, Viruses and Conditional lethal mutation.
DNA Transfer within and Between Bacterial Cells
In the second section of this lecture the educator described the DNA Transfer within and Between Bacterial Cells. DNA Transfer within and Between Bacterial Cells takes place by two methods that is by movement of Transposons or by transpositions and through programmed rearrangements.
Transposons are small parts of DNA that move readily from one side to another on to the Chromosomes and on to the plasmid. Transposons consist of Inverted repeats, they carry genes for transposition and structural genes. Movement of transposons from one side to other is called the Transposition. Transposition occurs through cut paste mechanism or copy paste mechanisms.
The Second method through which the bacteria transfer DNA with the genome is Programmed rearrangement. In this method the genes from the side of inactivation moves to the side of activation where they will express new proteins.
The method through which the bacterial cell is able to transfer its DNA from one cell to another one such method is Conjugation. In conjugation the transfer of DNA from donor bacterium to the recipient bacterium takes place when they come to physical contact. Process of conjugation is controlled by fertility plasmid. In high frequency recombination cells, Fertility Plasmid DNA is integrated into the bacterial chromosome and go through process of conjugation.
In this section the educator explains the Transduction in detail. Transduction is the process through which DNA is transferred by means of a bacterial virus known as bacteriophage. Bacteriophages are host specific viruses and they carry out their replication cycle with their host that is bacteria.
Lysogenic conversion is the term applied to the new properties that a bacterium acquires as a result of expression of the integrated prophage genes. There are two types of Transduction, Generalized transduction and specialized transduction. Generalized transduction is carried out by lactic phage’s and Specialized transduction is carried out by lysogenic phage’s.
In the fourth section of this lecture the educator explains the Transformation in detail. In Transformation, Transfer of DNA itself from one cell to another takes place. Transformation played a vital role is discovery of DNA as genetic material. In 1944 Non, encapsulated rough pneumococci transformed to encapsulated smooth pneumococci
There are two types of Transformation, Natural Transformation and Artificial Transformation. In Natural Transformation bacteria adapts to transfer DNA from one bacterium to another and for this process expression of multiple genes is required. In Artificial transformation, Transfer of rDNA to a competent bacterial cell under laboratory conditions takes place. Methods of making competent cells are CaCl treatment-Heat shock and Electroporation. Applications of Artificial Transformation are Cloning, to make multiple copies of DNA, to express large amount of proteins and enzymes and in the generation of cDNA libraries.
Transfection is the process of Injecting purified DNA into the nucleus of a eukaryotic cell. It is an important tool in genetic engineering.
In the last section of lecture the educator describes the Recombination, its definition and types. Recombination is the process through which Integration of the foreign DNA into host cell chromosome takes places. This process is facilitated by two Enzymes that are Endonucleases, and ligases. For Homologous recombination to occur there must be region of homology and similarity between the foreign DNA and incoming DNA and the existing and host cell DNA. Using homologous recombination other applications also carried out like it is important pathway in DNA repair and by using it Mutant Strain Production is also carried out. DNA repair mechanism involves homologous recombination.
Non-Homologous recombination is the process which occurs when the regions of homology not found, and the incoming DNA integrates randomly at any site into the chromosomes. Like homologous recombination, non-homologous recombination also plays its part in DNA repair mechanism.