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MICROBIOLOGY : MICROBIAL MOLECULAR BIOLOGY AND GENETICS

MICROBIOLOGY : MICROBIAL MOLECULAR BIOLOGY AND GENETICS

MICROBIAL MOLECULAR BIOLOGY AND GENETICS

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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 information is
not essential …

MICROBIAL MOLECULAR BIOLOGY & GENETICS

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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 foundations of classical genetics, bu…