Lesson 18. CLONING, TRANSGENIC ANIMALS, EMBRYO SEXING ETC
CLONING, TRANSGENIC ANIMALS, EMBRYO SEXING ETC
The success rate in terms of pregnancy establishment varies from 25-52% up to 19% pregnancies reach up to the term and 2-16% of embryos develop to healthy calves at weaving.
18.2.1 Applications of cloning
2. Cloning may also be useful in the production of research models. These models may or may not include genetic modifications.
3. Uses in agriculture include many applications of the technology which include:
b) Other purposes may range from "insurance" to making copies of cattle that have sentimental value, similar to cloning of pets.
c) Increased selection opportunities available with cloning may provide for improvement in genetic gain.
2 Cloning has additional obstacles to conquer. Social and regulatory acceptance of cloning is paramount to its utilization in production agriculture. Regulatory acceptance will need to address the animal, its products, and its offspring.
3 Loss of pregnancies due to developmental abnormalities. These abnormalities appear to be due to faulty epigenetic reprogramming ad gene expression in the genes of different cells.
18.3 Trans Genesis
Incorporation of foreign gene into the genome of an animal led to the development of the transgenic technology and the animal, thus produced is called as transgenic animal
18.3.1 Somatic cell nuclear cloning
18.3.2 Embryonic stem cell mediated gene transfer
18.3.3 Embryo micromanipulation and sexing
Most basic studies in maintaining embryos have been done in mice but application of these new techniques to large domestic animals will make them a powerful tool in animal breeding.
18.3.4 Applications of transgenic animals
A wide gamut of applications is possible which includes:
- Gene Pharming: Refers to the production of recombinant biologically active human proteins in the mammary glands of transgenic animals.
- Antibody production: Numerous monoclonal antibodies are being produced in the mammary gland of transgenic goats that can be employed both for diagnosis and treatment of diseases.
- Xenotransplantation: Producing transgenic animals to meet the demand for organs and tissues that need to be transplanted.
- Blood replacement: Here the whole idea is to produce functional human hemoglobin in transgenic animals.
- Disease model: The traditional lab experimental animal mouse differs in physiology, anatomy and life span from those of humans, therefore making it an inappropriate model for many human diseases. One the other hand, farm animals, such as pigs, sheep or even cattle, may be more appropriate models to study potential therapies for human diseases which require longer observation periods.
- Carcass composition: Transgenic animals are being produced, having significant improvements in economically important traits such as growth rate, feed conversion and body fat/muscle ratio.
- Lactation: Emphasis on transgenic animals with improved physicochemical properties of the milk. Hypoallergenic milk, milk with modified composition of casein are few examples.
- Eco-friendly: Environment friendly transgenic animals like creation of transgenic animals can convert certain pollutant materials into nonpolluting products.
- Wool production: To increase the amount and quality of fleece produced by animals.
- Disease resistance: To create transgenic animals that can resist diseases better.
Application of cloning, production of desirable animals by using transgenic technology and determination of sex of the embryo will increase the products with of the animals but the costs involved in their implementation were high and it takes some more time to reach to the field level.
18.4 Embryo Sexing
Fig. 18.3(a) Embryo sexing procedure
Fig. 18.4(b) Embryo sexing Procedure
18.4.1 Steps in embryo sexing
2 Selection of grade one or grade two embryos.
3 Embryo washed with PBS & placed in a drop containing 200 mM sucrose under micromanipulator.
4 Zona pellucida cut open with fine micro blade.
5 Few blastomere sucked with fine aspiration pipette.
6 Washed in KCl & transferred to Eppendorf tube.
18.4.2 Isolation of embryonic DNA
2 Overlaid with 25 μL of mineral oil
3 Incubated at 37°C for 10- 60 min
4 Inactivation of proteinase-K at 98°C for 10 min.
5 Cooled at 4°C
18.4.3 Amplification of DNA
2 Subjected to PCR cycling
3 3 min. denaturation at 94°C è 10 cycles of denaturation at 92°C è Annealing at 50°C (80 seconds) è Extension at 72°C for 20 seconds èFurther 40 cycles at 60°C of annealing temperature èFinal extension achieved by 5 min. incubation at 72°C
18.4.4 Identification of sex: It can be done by two approaches
2 Direct observation under UV light: tubes having male DNA show bright pink fluorescence.
2 Sanjeev Sharma*, Aarti Bhardwaj$, Shalini Jain# and Hariom Yadav# *Animal Genetics and Breeding Division, #Animal Biochemistry Division, National Dairy Research Institute, Karnal-132001, Haryana, India $College of Applied Education and Health Sciences, Meerut, U.P. Source: Internet PowerPoint presentation
3 Venkatesh M.N. Research Journal Of BioTechnology Vol. 3 (1) Feb. (2008)
Res. J. Biotech.
1. Singh BD (2007), Biotechnology Third edition, Kalyani Publishers, New Delhi
2. Kumar HD (2003), Modern concepts of Biotechnology, Vikas publishing house pvt ltd.