To express a cloned gene (for a desired product) in a transformed cell means that it has to transcript and translate. Sometimes functional proteins are produced by post-translation modifications. Protein synthesis is based on the encoded information in the sequence of the DNA strand bases. Structural gene directs the cells machinery for sequential linear arrangements
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The HRT method is utilised for recombinants without introns. The most difficult step in applying hybridisation is obtaining a suitable probe. If the target DNA is represented with highly abundant mRNA, a small number of cDNA clones can be screened and the target gene can be identified by sequencing or hybrid released translation. In HRT,
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The replica plate method is used in genetic engineering for identifying transformed bacterial cells (cells containing foreign DNA). Only some of the cells transformed with a specific DNA may actually have foreign DNA. Thus, it is essential to screen those cells having foreign DNA by the technique of colony hybridisation (only for bacterial cells) figure.
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For conventional DNA sequencing templates of signal stranded DNAs are used. PCR-based methods can be employed to manufacture them. Also vectors based on certain bacteriophages whose genomes assume a single stranded DNA at some stages in their life cycle can be used. M13 Bacteriophage M13 is a filamentous bacteriophage. Its genomes bear single-stranded circular DNA
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Human and other mammalian genomes are very large, therefore, vectors are needed to clone large DNA fragments. Many vectors have been prepared that aid in the characterisation and expression of large genes or gene complexes. These vectors exhibit varied cloning capacity (table). Table Maximum DNA Insert Possible with Different Cloning Vectors Vectors Hosts Insert Size
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Cloning vector is a DNA molecule in which when a foreign DNA is integrated achicves the capability to replicate it within itself to produce many clones of recombinant DNA. Characteristics of a Cloning Vector Its size should be small. It should bear the capability to self-replicate within the host cell. It should carry a restriction
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The target DNA or the DNA insert isolated and enzymatically cleaved by the selective restriction endonuclease, are ligated (joined) through the action of ligase enzyme to the vector DNA. As a result, an rDNA molecule known as cloning-vector-insert DNA construct is produced. Direct Ligation of Cohesive Termini (DNA Ligase) The target gene can be inserted
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In recombinant DNA (rDNA/rec DNA) technology, DNA molecules from two different sources are joined and inserted into a host organism to get products useful for human use (figure). A clone refers to a group of cells or organisms obtained from one progenitor, thus indicating that the members of a clone are genetically same. This is
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The process of developing proteins having desired functions by manipulating their stability and specificity is termed protein engineering. This can be done by taking two main approaches, rational design and irrational design (or directed evolution). In the former case, knowledge of the protein structure and function is considered and a rational gene mutation is planned.
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Genetic engineering involves deliberate DNA manipulation in organisms to alter their genes. Although the organisms whose genes are being altered may not be microbes, but the substances and techniques involved are obtained from microbes and adapted for use in more complex organisms. Historical Background The term genetic engineering initially was used for various techniques used
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