8 Biotechnology- Biology for Human Welfare
8.3 Transgenic Animals
Transgenic animals
Dr V Malathi
Animals that have had foreign genes purposefully added to their genomes are known as transgenic animals. These genes, also referred to as transgenes, are inserted to imitate human diseases, enhance livestock, create medications, or investigate gene function. Usually, genetic engineering methods are used to create transgenic animals.
While bacteria can successfully create a number of recombinant proteins used in medicine, some proteins require a eukaryotic animal host in order to be processed properly. As a result, genes have been cloned and expressed in mice, sheep, goats, and chickens. Transgenic animals are those that have been modified to express recombinant DNA.
Steps to Produce Transgenic Animals
1.Identification and Isolation of the Gene
A donor organism—such as bacteria, plants, or animals—is used to identify a particular gene of interest.
In order to guarantee expression in the intended organism, the gene is extracted and prepared with regulatory sequences, including a promoter and a terminator.
2.Preparation of the Vector
To make it easier for the gene to enter the animal’s genome, it is placed into a vector (such a plasmid or viral vector). To regulate the location and timing of gene expression, regulatory sequences are incorporated, such as constitutive or tissue-specific promoters.
3. Gene Transfer Techniques
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- Microinjection :A thin glass needle is used to inject the gene straight into the pronucleus of a fertilized egg.To create a transgenic animal, the altered egg is inserted into a surrogate mother. For instance, transgenic mice are used in biomedical research.
- Gene Transfer Mediated by Retroviruses : The desired gene is inserted into a retrovirus that infects embryonic cells. Stable expression is ensured by the virus’s integration of the gene into the host DNA.
- Embryonic Stem (ES) Cell-Mediated Gene Transfer : In vitro, the transgene is inserted into embryonic stem cells.Early-stage embryos are then placed into a surrogate mother after modified stem cells have been added.
In order to produce fully transgenic animals, additional breeding may be necessary if the progeny are chimeric. - Gene editing using CRISPR-Cas9 CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) are the repeated DNA sequences found in bacterial genomes. They serve as a memory of past viral infections by storing fragments of viral DNA which are called spacers.The ground-breaking gene-editing tool CRISPR-Cas9 is based on a defense system naturally present in bacteria and archaea. It enables the precise addition, deletion, or change of particular genetic sequences to an organism’s DNA. Because of CRISPR-Cas9’s effectiveness, adaptability, and relative simplicity, it has emerged as a key component of modern biotechnology.
- Sperm-Mediated Gene Transfer (SMGT) : Sperm cells are used as carriers to transfer foreign DNA into an egg during fertilizati