05-30-2008, 07:45 PM
Bacterial genetics
1)-Transformation : DNA taken up directly from environment by competent prokaryotic and eukaryotic cells. Any DNA can be used.
2)Conjugation
F+ × F“
F+ plasmid contains genes required for conjugation process. Bacteria without this plasmid are termed F“. Plasmid is replicated and transferred through pilus from F+ cell. Plasmid DNA only; no transfer of chromosomal genes.
Hfr × F“
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed Hfr cell. Replication of incorporated plasmid DNA may include some flanking chromosomal DNA. Transfer of plasmid and chromosomal genes.
3)Transduction
*Generalized
Lytic phage infects bacterium, leading to cleavage of bacterial DNA and synthesis of viral proteins. Parts of bacterial chromosomal DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.
*Specialized
Lysogenic phage infects bacterium; viral DNA incorporated into bacterial chromosome.
When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage viral capsid and can infect another bacterium.
4)Transposition
Segment of DNA that can œjump (excision and reincorporation) from one location to another, can transfer genes from plasmid to chromosome and vice versa. When excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium.
5)-Lysogeny
Genetic code for a bacterial toxin encoded in a lysogenic phage. ABCDE
ShigA-like toxin .
Botulinum toxin (certain strains)
Cholera toxin
Diphtheria toxin
Erythrogenic toxin of Streptococcus pyogenes
1)-Transformation : DNA taken up directly from environment by competent prokaryotic and eukaryotic cells. Any DNA can be used.
2)Conjugation
F+ × F“
F+ plasmid contains genes required for conjugation process. Bacteria without this plasmid are termed F“. Plasmid is replicated and transferred through pilus from F+ cell. Plasmid DNA only; no transfer of chromosomal genes.
Hfr × F“
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed Hfr cell. Replication of incorporated plasmid DNA may include some flanking chromosomal DNA. Transfer of plasmid and chromosomal genes.
3)Transduction
*Generalized
Lytic phage infects bacterium, leading to cleavage of bacterial DNA and synthesis of viral proteins. Parts of bacterial chromosomal DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.
*Specialized
Lysogenic phage infects bacterium; viral DNA incorporated into bacterial chromosome.
When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage viral capsid and can infect another bacterium.
4)Transposition
Segment of DNA that can œjump (excision and reincorporation) from one location to another, can transfer genes from plasmid to chromosome and vice versa. When excision occurs, may include some flanking chromosomal DNA, which can be incorporated into a plasmid and transferred to another bacterium.
5)-Lysogeny
Genetic code for a bacterial toxin encoded in a lysogenic phage. ABCDE
ShigA-like toxin .
Botulinum toxin (certain strains)
Cholera toxin
Diphtheria toxin
Erythrogenic toxin of Streptococcus pyogenes