MICROBIOLOGY

MICROBIOLOGY : MICROBIAL MOLECULAR BIOLOGY AND GENETICS

MICROBIOLOGY : MICROBIAL MOLECULAR BIOLOGY AND GENETICS

MICROBIAL RECOMBINATION AND PLASMIDS: Bacterial Plasmids:  Conjugation, the transfer of DNA between bacteria involving direct contact, depends on the presence of an “extra” piece of circular DNA known as a plasmid. Plasmids play many important roles in the lives of bacteria. They also have proved invaluable to microbiologists  and  molecular  geneticists  in  constructing  and  transferring new genetic combinations and in cloning genes. Plasmids are small double-stranded DNA molecules, usually circular, that can exist independently of host chromosomes and are present in many bacteria (they are also present in some yeasts and other fungi). They have their own replication origins and are autonomously replicating and stably inherited. A replicon is a DNA molecule or sequence that has a replication origin and is capable of being replicated. Plasmids and bacterial chromosomes are separate replicons. Plasmids have relatively few genes, generally less than 30. Their genetic info

MICROBIAL RECOMBINATION AND PLASMIDS: In a general sense, recombination is the process in which one or more nucleic acids molecules are rearranged or combined to produce a new nucleotide sequence. Usually genetic material from two parents is combined to produce a recombinant chromosome with a new, different genotype. Recombination results in a new arrangement of genes or parts of genes and normally is accompanied by a phenotypic change. Most eucaryotes exhibit a complete sexual life cycle, including meiosis, a process of extreme importance in generating new combinations of alleles (alternate forms of a particular gene) through recombination. These chromosome exchanges during meiosis result from crossing-over between homologous chromosomes, chromosomes containing identical sequences of genes . Until about 1945 the primary focus in genetic analysis was on the recombination of genes in plants and animals. The early work on recombination in higher eucaryotes laid the foun