Share Your PPT File. About1.7 x 105 colonies ofthe M. leprae gene libraries in pEX1, pEX2, and pEX3 were screenedwiththeabsorbedcontact serumpool. The genes in this genome include the replication gene for DNA/RNA of the phage and the gene for protein coat. The colonies which grow, can be said to have a plasmid, as the antibiotic resistance gene of plasmid enables the bacteria to grow. It should be relatively small and should replicate in a relaxed fashion. The above features ease the direct selection of recombinant cells. When RNA-RNA hybridization occurs, it can be called eastern blot. (g) The yeast cells of Saccharomyces cerevisiae are transformed by treatment with lithium chloride or lithium acetate. (j) An alternative method of introducing any DNA into any of the living cells is by microinjection, using a fine syringe, DNA molecules are directly injected into the nucleus of the cell to be transformed. What is the reserve food material in red algae? Weselected 36 potentially positive recombinants. Selection of Restriction Endonucleases: Step # 4. All these procedures are based on two basic themes: This is just like marker selection procedure, described above, where selection occurs directly in the culture plate itself by the detection of the presence of the protein product of that gene. For this each cell is cloned separately and different procedures are adopted to select the desired clone. Putative recombinant clones were selected on LB agar medium supplemented with kanamycin (50 mg/ml) and 5% sucrose. The alpha-2 collagen gene of chicken is 38 Kb. There are different types of vectors which can be used to clone fragments of foreign DNA and propagate (clone) them in a suitable host. The maximum size of the DNA that can be introduced into any plasmid is 5 kb and that for bacteriophage Ml3 is less than 3 Kb. Before you continue with your experiment, colonies must be screened for positive results. The A and B chains are then extracted from the β-galactosidase fragment and purified. (b) A DNA probe can be synthesized chemically with a complementary sequence to the desired gene and used to hybridize the DNA from each clone. A single transformed cell grows to give rise to a colony (Fig. Content Guidelines 2. beta-globin gene mRNA is obtained by lysing the reticulocytes and the polyribosomes are collected by centrifugation and treated with antibody specific for this protein. 63 nucleotides are required for synthesizing the chain A and 90 for the B chain, plus a codon at the end of each chain, signalling the termination of protein synthesis. The steps are: 1. Step # 2. Introduction of the rDNA into a Host Cell 6. Various methods are adopted for introduction of the different vectors into different hosts. (i) rDNA formation by the use of restriction endonuclease creating sticky ends: To join together two duplex DNAs from different species, the two DNAs are separately acted upon by the same restriction endonuclease (BamHI) giving staggered (cohesive/sticky) two stranded cut. Selection of Restriction Endonucleases 4. (a) Direct Selection of Recombinant Clones: A recombinant clone can be selected with the help of marker genes present in the vector as well as in the donor DNA. This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Transfer of Recombinant DNA into Bacterial Cell: Technique # 4. Selection of a Suitable Cloning Vector DNA or Vehicle DNA: Step # 3. The phenotypes conferred by different plasmids are: iii. This ultraviolet absorbance can also be used to check the purity of a DNA wherein the ratio of DNA absorbance at 260 nm and 280 nm (A260/A280) is 1.8. Some commonly used plasmids as vectors for the preparation of recombinant DNA are-pMB-9, pBR- 322, pBR-325, pKC-7, pAC-4, C-184, pAC-105, pMK-16, pMF-3, pBRHl, pUB-110, and pCB-16. Some of the M13 vectors are M13 mp2, M13 mp5, fdlOl, fdl07, fd-tet. i. the rDNA. Production of restriction and modification enzymes. (f) Transfection can also be done by packaging the phage DNA into the mature lambda phage particle and then infecting the bacterial cells with it. Bacteriophages are commonly known as phages. (8) Recombinant vaccines can be produced by rDNA technology. If the cloned DNA itself codes for resistance to the antibiotic ampicillin (amp r) the recombinants can be allowed to grow on minimal medium containing ampicillin.Only such recombinants will grow and form colony on medium that contain amp r gene on its plasmid vector.. Selection of Target DNA 2. Content Guidelines 2. From this gene library any one gene, which is commercially important i.e. Introduction of the rDNA into a Host Cell: Step # 6. Disclaimer Copyright, Share Your Knowledge In some cases, the transformation of protoplast is stimulated by a special technique called electroporation. Among eukaryotes, DNA cloning has been done in yeast, mouse and in higher plant species. E. coli cells are normally sensitive to the antibiotic ampicillin and tetracycline i.e. Hence the bacteriophage lambda genome was modified by Collins and John in 1978 by deleting some bases and introducing single stranded complementary extension sequences at the ends of its DNA molecule called the Lambda Cos site, in order to facilitate insertion and cloning of large DNA molecules. VANRENS,LINDAF. Inside the cell the DNA synthesizes a complementary strand and becomes the double stranded intermediate known as the replicative form (RF). The action of some endonucleases gives DNA fragments with sticky/cohesive ends whereas others give blunt ended DNA fragments. The genes for the following proteins are generally cloned i.e. Target DNA is selected considering the following points: (a) It should be easily extractable from its source of natural existence. Procedure for Production of Recombinant DNA (rDNA): (a) Preparation of Cloning Vector-insert DNA Constructs: (b) Preparation of Complementary DNA (cDNA): Step # 5. The complete human genomic DNA is cleaved into about 7,00,000 pieces by the action of the restriction endonuclease and all of these DNA fragments can be inserted into a cosmid and such an insert containing all the genomic DNA of an organism is called genomic library. The trans­formed cells can be plated on selection medium containing different antibiotics. Small size so as to accommodate the eukaryotic DNA fragments of 40-45 kb in length. (h) Calcium phosphate, DEAE dextran and protoplast fusion are used to introduce DNA into the ani­mal cells.