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In molecular biology, [1] [2] [3] DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. [4] DNA replication occurs in all living organisms acting as the most essential part of biological inheritance .
Bacterial recombination is a type of genetic recombination in bacteria characterized by DNA transfer from one organism called donor to another organism as recipient. This process occurs in three main ways: Transformation, the uptake of exogenous DNA from the surrounding environment. Transduction, the virus-mediated transfer of DNA between bacteria.
In genetic engineering, recombination can also refer to artificial and deliberate recombination of disparate pieces of DNA, often from different organisms, creating what is called recombinant DNA. A prime example of such a use of genetic recombination is gene targeting , which can be used to add, delete or otherwise change an organism's genes.
Molecular cloning takes advantage of the fact that the chemical structure of DNA is fundamentally the same in all living organisms. Therefore, if any segment of DNA from any organism is inserted into a DNA segment containing the molecular sequences required for DNA replication, and the resulting recombinant DNA is introduced into the organism from which the replication sequences were obtained ...
Finally, one copy of the genomes is segregated into each daughter cell at the mitosis or M phase. [2] These daughter copies each contains one strand from the parental duplex DNA and one nascent antiparallel strand. This mechanism is conserved from prokaryotes to eukaryotes and is known as semiconservative DNA replication.
As the DNA double helix is unwound by helicase, replication occurs separately on each template strand in antiparallel directions. This process is known as semi-conservative replication because two copies of the original DNA molecule are produced, each copy conserving (replicating) the information from one half of the original DNA molecule.
On contact with the intein-free copy, the HEG domain initiates the DNA double-stranded break repair mechanism. This process causes the intein sequence to be copied from the original source gene to the intein-free gene. This is an example of protein directly editing DNA sequence, as well as increasing the sequence's heritable propagation.
During logarithmic growth, a DNA damage in one chromosome may be repaired by HRR using sequence information from the other homologous chromosome. Once cells approach stationary phase, however, they typically have just one copy of the chromosome, and HRR requires input of homologous template from outside the cell by transformation. [41]