* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Microbial Genetics
Oncogenomics wikipedia , lookup
Metagenomics wikipedia , lookup
DNA polymerase wikipedia , lookup
Human genome wikipedia , lookup
Bisulfite sequencing wikipedia , lookup
Mitochondrial DNA wikipedia , lookup
Transposable element wikipedia , lookup
Minimal genome wikipedia , lookup
Zinc finger nuclease wikipedia , lookup
Primary transcript wikipedia , lookup
Genome (book) wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
Cancer epigenetics wikipedia , lookup
Genealogical DNA test wikipedia , lookup
United Kingdom National DNA Database wikipedia , lookup
DNA damage theory of aging wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Point mutation wikipedia , lookup
Genome evolution wikipedia , lookup
Nucleic acid double helix wikipedia , lookup
DNA vaccination wikipedia , lookup
Epigenomics wikipedia , lookup
Cell-free fetal DNA wikipedia , lookup
DNA supercoil wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Molecular cloning wikipedia , lookup
Non-coding DNA wikipedia , lookup
Genomic library wikipedia , lookup
No-SCAR (Scarless Cas9 Assisted Recombineering) Genome Editing wikipedia , lookup
Genetic engineering wikipedia , lookup
Genome editing wikipedia , lookup
Designer baby wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Microevolution wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Microbial Genetics Genetic transfer and recombination Genetic recombination Genetic recombination through sexual reproduction is an important means of variation in eukaryotes Prokaryotes do not have an equivalent process of sexual reproduction However, prokaryotes do have mechanisms by which DNA can be transferred between strains of the same species, or even between different species Contributes to a population’s genetic diversity Gene transfer Vertical gene transfer Occurs during reproduction. Transfer of genes from an organism to its offspring Horizontal gene transfer Transfer of genes from one organism to another within the same generation Horizontal gene transfer Involves one way transfer from a donor cell to a recipient cell A recipient cell that incorporates DNA from the donor is called a recombinant Genes are transferred naturally between bacteria by three mechanisms Transformation: DNA is transferred as “naked” DNA Conjugation: DNA is transferred between bacteria that are in contact with each other Transduction: DNA is transferred by a bacterial virus (bacteriophage) Homologous recombination DNA introduced into bacteria usually does not have a mechanism to replicate itself It relies on integration into the genome of the host bacterium in order to survive and be passed on Incoming DNA Host genome Recombinant genome gene A gene Z gene C gene A gene B gene C gene A gene Z gene C Griffith’s experiment, 1928 Streptococcus pneumoniae “Naked” DNA When a bacterial cell lyses, it releases its DNA into the environment Transformation DNA is transferred as naked DNA DNA breaks into pieces on cell lysis DNA is taken up by the recipient cell A region of the recipient DNA is replaced by the donor DNA (recombination) Unrecombined DNA is degraded Transformation occurs naturally in very few genera of bacteria Bacillus, Haemophilus, Neisseria, Acinetobacter, and some strains of Streptococcus and Staphylococcus. The recipient cell must be in a physiological state to take up DNA. Changes in the bacterial cell wall make it permeable to large DNA molecules Some bacteria, which are not normally can be made so in laboratory Conjugation DNA transfer between two bacteria that are in contact with one another Contact between donor and recipient cells is initiated by sex pili DNA is transfer through a conjugation bridge or open pore between donor and recipient cell Mediated by a plasmid, called an F-factor (fertility factor) or a conjugative plasmid Plasmids Small, circular molecules of DNA Replicate independently of the chromosome Usually dispensable for growth, but under some conditions provide a selective advantage such as antibiotic resistance or a unique metabolic pathway Conjugative plasmids: carry genes for conjugation including sex pili Mechanism of conjugation Donor contacts recipient, attaches using sex pilus F-factor initiates transfer of a copy of itself Recipient is converted to a new donor cell Importance of plasmids Providing a selective advantage Enhancing pathogenicity Some Pseudomonas sp. have plasmid encoded enzymes to degrade petroleum allowing them to live in fuel tanks or fuel spills The E. coli strain causing infant or traveler’s diarrhea carries plasmids for toxin production and bacterial attachment. Antibiotic resistance Many antibiotic resistance genes are carried on plasmids which can be rapidly transferred to other bacteria, resulting in widespread resistance to antibiotics and strains that resistant to multiple antibiotics such as methicillin-resistant Staphylococcus aureus or Golden Staph Transduction Mediated by a bacterial virus (bacteriophage or phage) DNA from the donor is transferred to the recipient inside the phage particle Two types of transduction Generalized Specialized Generalized transduction Donor cell is infected with a phage Donor DNA is incorporated into the phage (transducing phage) The donor cell lyses The transducing phage infects the recipient cell and injects the donor DNA DNA integrated into the genome Transposons Segments of DNA that can move from one region of DNA to another and integrate through nonhomologous recombination Contain information for their own transposition Transposase enzyme for cutting and resealing DNA Short terminal repeats which the transposase recognizes as recombination sites Insertion sequences are the simplest transposons Complex transposons carry other genes e.g., antibiotic resistance genes Natural history of a transposon chromosome transposon plasmid Genomes of bacteria are elastic Bacterial genomes are often receiving genetic information from other bacteria through genetic transfer and recombination In the same way that mutations can be beneficial, neutral or harmful, so is the recombination of incoming DNA New gene combinations are maintained if they provide the organism with a selective advantage