Gene replacement refers to a technique which utilizes homologous recombination (Carter & Shieh, 2010, p. 265), to make alterations by either adding a gene, deleting a gene or including point mutations. Gene replacement attempts to cure most of the genetic diseases at molecular level. A successful gene replacement prevents a protein from causing harm, giving new functions to proteins, and recovering or enhancing the normal function of a protein. This technique is commonly used to prevent, treat or improve animals. This is a permanent process that is very beneficial to animals. The process of animal gene replacement involves several processes like gene construction, restriction digestion, ligation, transformation, and transfection. Screening is then done to check on the recombinant animal cells.
Gene construction refers to an artificially made DNA segment of interest that is usually inserted in an animal cell. Therefore, for animal gene replacement, gene construction is the initial process performed to enable the artificial nucleic acid segment to be inserted to an animal. The constructed gene often has a DNA sequence that encodes a desirable protein (Marx, 1989, p. 12). Furthermore, the gene construct may also inhibit some genes expressions, allow expression of mutant or wild-type proteins. This process involves identification of a desirable gene from another DNA sequence of another organism. Then restriction enzymes are usually used to cut this DNA segment. The enzyme is known as restriction endonucleases and cuts the desired segment at specific sites. Restriction endonuclease will recognize specific segments (Styne, 2004, p. 2). For instance, it may recognize GATATC sequence in a DNA molecule.
The restriction digestion involves mixing a DNA molecule with restriction endonucleases in a buffer. Care is normally taken during this process to avoid denaturing of the restriction enzyme and the DNA. Once the gene of interest has been obtained, it is usually joined in the DNA sequence of a vector through ligation. According to Williams (2000, p. 146), vector acts like a carrier of the desirable gene. In ligation, DNA ligase enzyme is used to join the animal DNA with the gene of interest, enabling a transformation. Transformation involves incorporation of exogenous DNA to an animal cell. It is done via injection of the vector to the animal. Transfection involves making holes in the animals’ cell membrane so that the vector can be taken in. This process is normally done by electroporation, utilizing calcium phosphate or through the production of liposomes that fuse with animal’s cell membrane to enable transmit.
The recombinant animal is then cloned to produce genetically identical recombinant animals. There are several screening methods used (Fairbanks, 2004, p. 165). They include blue-white screening, colony PCR, and sequencing. Screening of the recombinant animal cell method commonly used is polymerization chain reaction, which is used to check on the DNA itself. If gene expression is encoded by sequences or rDNA, the recombinant gene can easily be detected using western hybridization or Rt-PCR. The basis of screening is to ensure that the process of gene replacement was successful and effective
Gene replacement depends on identifying a dependable delivery system to transmit the desirable gene to the target cells. The transmitted gene should work well within the target cells without bringing harm to the animal. As much as there are researchers and scientists face the challenge of delivering genes which will work well (“Gene Therapy - A Revolution in Progress: Human Genetics and Medical Research”, n.d.), they are still performing gene replacement to animals successfully. The process of gene replacement is very advantageous in both medicine and agriculture. In medicine, it has been applied in gene therapy for sickle cell anemia as well as other blood disorders. In agriculture, it is broadly applied so as to improve animals’ health and increase their products. Gene replacement in animals such as cows has enabled healthier cows and more
milk production. Also, gene replacement has enabled researchers to identify several genes as well
as their function. Gene therapy involves introducing DNA molecules into animal cells which lead to making of beneficial proteins or compensating for the abnormal genes.
References
Carter, M., & Shieh, J. C. (2010). Guide to research techniques in neuroscience. Amsterdam: Elsevier/Academic Press.
Fairbanks, S. D. (2004). Cloning: Chronology, abstracts, and guide to books. New York: Nova Science Publishers.
Gene Therapy - A Revolution in Progress: Human Genetics and Medical Research. (n.d.). Retrieved from https://history.nih.gov/exhibits/genetics/sect4.htm
Marx, J. L. (1989). A Revolution in biotechnology. Cambridge [Cambridgeshire: Cambridge University Press.
Styne, D. M. (2004). Pediatric endocrinology. Philadelphia: Lippincott Williams & Wilkins.
Williams, G. (2000). Advanced biology for you. Cheltenham: Thornes.
