Biotechnology is the use of microbes to make practical products. The top three j
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Question
Biotechnology is the use of microbes to make practical products. The top three justifications for manipulating the genomes of cells are:
1. to eliminate undesirable phenotypic traits in humans, animals, plants and microbes.
2. to combine the beneficial traits of two or more organisms to create a new more valuable organism.
3. to create cells that synthesize products humans need.
Recombinant DNA technology employs a number to tools and techniques to isolate genes and insert them into cells grown in culture. The following are five tools of recombinant DNA technology and examples of application of the tools.
Mutagens are physical and chemical agents that produce mutation. Some mutations are beneficial, so creating a large number of mutations increases the probability of discovering a beneficial mutation. For example the fungus Penicillium may be mutated to syntheisize a more effective antibiotic. Mutagens include uv radiation and ionizing radiation. Mueller first demonstrated the effects of X rays on Drosophilia, establishing cause and effect between radiation and genetic changes manifested in phenotypic changes. Chemical mutagens in bacteria may be carcinogenic in humans. The Ames test utilizes bacteria to test for mutagenic activity, and identify chemicals that may induce cell changes that lead to cancer. Ethidium bromide which may be used to visualize DNA on gel, is also a mutagen because it disrupts base pairing.
1. Explain and describe one physical and one chemical mutagen and its application.
Reverse transcriptase synthesizes cDNA from mRNA, which is the reverse of information flow as depicted in the central dogma of molecular biology, i.e. DNA is transcribed to RNA which is translated to peptides. Cells may have millions of copies of mRNA, so being able to synthesize the complementary DNA reveals the gene that is being expressed. In addition, cDNA contains no introns because of processing in the eukaryotic transcription, so that cDNA may be inserted into a prokaryotic cell and may be translated into the corresponding peptide.
2. Explain how reverse transcriptase differs from RNA polymerase. Give one example of an application of reverse transcriptase in recombinant DNA technology.
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Explanation / Answer
Mutagens as defined above have potential to change the phenotypic expression of gene through chemical interaction with basic structure of gene. Here are the few examples of physical as well as chemical mutagens. These can be further divided into subcategory based on their mechanism of action;
Chemical mutagens
1. Mutagen changing the specificity of hydrogen bond:-
Nitrous Oxide (It converts the amino group into keto group). This deamination of adenine forms the hypoxanthine.
2. Alkylation:-
Dimethyl sulphate, Ethyl methane sulphonate. These chemicals create the gap in sequence after removal guanine or cytosine. After gap synthesis in gene sequence the incorrect base addition may cause the transversion or transition mutation.
Physical Mutagen:-
Radiations having wavelength below 340nm cause the damage to DNA. These rays are UV-rays, X-rays, alpha and beta rays etc.
Reverse transcriptase: - It helps in synthesis of complementary DNA from RNA molecule. This enzyme could be isolated from retroviruses. IN case of recombinant DNA technology the reverse transcriptase plays very important role, especially in case of AIDS where the reverse transcriptase provide the primer and helps in work related with virus. Reverse transcriptase helps in study of gene expression also with the help of RT-PCR technique.
RNA polymerase carry the synthesis of RNA from the DNA template, process is known as transcription.
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