Bacterial Genetics and Gene Transfer PDF

Bacterial Genetics and gene transfer 1  Lecture ILOs By the end of this chapter, students should be able to:  Identify bacterial genome  Describe bacteriophage, its structure, differentiate between its types  Describe plasmids, their function...

Bacterial Genetics and gene transfer 1  Lecture ILOs By the end of this chapter, students should be able to:  Identify bacterial genome  Describe bacteriophage, its structure, differentiate between its types  Describe plasmids, their function and classify them.  Compare phenotypic and genotypic variations.  Recognize different methods of gene transfer  The bacterial genome  is the total set of genes present inside the bacteria include  1- Essentially single circle bacterial chromosome contain essential structure gene 2- Additional genes may be carried or not I. Plasmids extrachromosomal circular DNA I. Bacteriophage DNA 3  Plasmids Extrachromosomal double-stranded, circular DNA Carry genes for non essential genes code non essential bacterial character 4 5  Conjugative = transmissible plasmids F-plasmid=Fertility plasmid= transmissible plasmid contain tra gene that code for formation of sex pilus Bacteria contain F plasmid called F + cell Sex pilus = bridge between bacteria for gene transfer by conjugation 6 Sex Pilus 7  Functions of plasmids (1) Fertility plasmid (F-plasmid) : they carry the F factor which can mediate gene transfer by conjugation (2) Drug resistance (R. factor plasmids): Genes coding for drug resistance of many bacteria are carried on plasmids. (3)Virulence plamids: Some plasmids carry genes whose products are the virulence factors (Pilli---Toxins) of some pathogenic organisms. 8 Bacterial Gene Transfer 9 Vertical gene transfer Genetic information passed from bacteria to its (daughters) offspring from generation to another generation = reproduction Horizontal gene transfer Bacteria transfer genetic information form one organism to another in the same generation leading to change in its character  GENE TRANSFER There are 3 types of gene transfer from one bacterium to the other leading to change in its character by 3 methods 1. Transformation: free bacterial DNA in media is taken up by another bacteria May be induced in laboratory 2-Conjugation: bacteria donor contain F plasmid contact to recipient bacteria by sex pilus result in plasmid or part of chromosome can transferred 3-Transduction: Transfer of DNA from bacteria to another by bacteriophage 12  Transformation Naked piece of DNA released from donor bacteria are taken up directly by recipient bacteria. from the surrounding medium. Bad news = DNA is naked and may be destroyed by nuclease 13  Conjugation It is mating of two bacterial cells. F + Bacteria contain F plasmid, which carries the genes (tra gene) that code for formation of sex pilus which bridges between Two bacterial cells. At the end two F+ cell produced If plasmid transferred 14 15 16 Plasmid transfer Conjugation occurs between an F+ cell and an F- cell. Sex pilus, connects the two cells. At the end two F+ cell produced 17 Application of bacterial gene transfere 1-genetic engineering and gene cloning 2-idea about transfer of drug resistance 18