Transcript Genetics
Batterjee Medical College Batterjee Medical College Bacteria Genetics Ass. Prof. Dr. Manal El Said Head of Microbiology Department Batterjee Medical College Bacteria Genetics • Bacteria have only one copy of their genome DNA, i.e., they are haploid. • Eukaryotic cells have two copies of their genome DNA, i.e., they are diploid. • Bacterial DNA is circular; human nuclear DNA is linear. Batterjee Medical College Transfer of DNA Within Bacterial Cells Transposons • Transposons are small pieces of DNA that move readily from one site on bacterial chromosome to another or from bacterial chromosome to plasmid. • They carry antibiotic resistance genes. • Transfer of transposons on plasmids to other bacteria by conjugation contributes to antibiotic resistance. Batterjee Medical College Transfer of DNA Within Bacterial Cells Programmed rearrangements: are movement of genes from inactive ( storage) sites into active sites where they are expressed as new proteins. • Bacteria can acquire new proteins (antigens) on their surface and evade the immune system e.g. Neisseria gonorrhoeae & Trypanosoma brucei Batterjee Medical College Transfer of DNA between Bacterial Cells The transfer of genetic information from one cell to another can occur by Conjugation Transduction Transformation Batterjee Medical College Transfer of DNA between Bacterial Cells: Conjugation • Conjugation: DNA (plasmid carrying antibiotic resistance gene or chromosomal) is transferred from one bacterium to another. • Donor bacterium have "fertility" plasmid (F plasmid). • Pilin protein forms sex pilus (conjugation tube). • DNA transferred by conjugation to recipient bacterium is a new copy that allows donor to keep a copy of DNA. Batterjee Medical College Transfer of DNA between Bacterial Cells: Transduction • It is process by which DNA (plasmid or chromosomal) is transferred from one bacterium to another by virus. • Transferred DNA integrates into chromosomal DNA of recipient & new proteins, such as exotoxins, are made- a process called lysogenic conversion. Batterjee Medical College Transfer of DNA between Bacterial Cells: Transformation Transformation is the process by which DNA itself, either DNA released from dying cells or DNA purified in the laboratory, enters a recipient bacterium. Batterjee Medical College Transfer of DNA between Bacterial Cells Comparison of Conjugation, Transduction & Transformation Transfer Process Procedure Conjugation Type of Cells Nature of DNA Transferred Involved DNA transferred Prokaryotic from one bacterium - Chromosomal - plasmid to another Transduction DNA transferred by Prokaryotic virus from one cell -Generalized transduction: Any gene to another -Specialized transduction: Only certain genes Transformation Purified DNA taken -Prokaryotic up by a cell -Eukaryotic Any DNA