Livestock (1993) / Chapter Skim
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4 New Technology and Its Impact on Conservation
4 New Technology and Its Impact on Conservation
Pages 77-96
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From page 77... ...
This chapter describes new and emerging technologies to quantify genetic variation, to transfer genes from one animal to another, and to optimize reproduction. With further development, many of these technologies could provide powerful tools for preserving and using livestock genetic resources.
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From page 78... ...
These methods include DNA (deoxyribonucleic acid) sequencing, DNA-DNA hybridization, protein electrophoresis, immunologic methods, and restriction fragment length polymorphisms (RFLPs)
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From page 79... ...
,., , i. Restriction fragment length polymorphisms from five individuals in a population of crossbred cattle are revealed using two different restriction enzymes (EcoRI and BamHI)
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From page 80... ...
When genomic DNA is cut with one of these enzymes (more than 100 are commercially available) , a mixture of DNA fragments of varying sizes results; these are called restriction fragments.
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From page 81... ...
, bind to complementary DNA fragments on the filter. Positions of the probes, which correspond to specific restriction fragments, can be determined using autoradiography.
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From page 82... ...
Applications of RFLP-assisted mapping to human genetics are reviewed by Watkins (1988~. More than 4,500 loci have been cataloged for the human genome, and the number is rapidly increasing (Human Gene Mapping 10, 1989~.
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From page 83... ...
Genomic DNA and DNA libraries from different genetic sources also represent valuable research resources. Establishing an Animal Genomic Library An animal genomic library is a collection of cloned fragments representative of individual genomes.
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From page 84... ...
These colonies represent individual "cloned" segments of DNA. Screening an Animal Genomic Library Screening a genomic library is the process of discovering which colony contains a particular DNA segment.
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From page 85... ...
The DNA sequences can then be separated from the virus DNA using the same endonuclease originally employed in constructing the library. To isolate a single gene it may be necessary to obtain DNA segments from more than one-colony because intact genes are rarely found in a single clone.
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From page 86... ...
In certain situations, however, preservation of DNA stores may be a reasonable and useful supplement to other efforts. For example, a sufficient DNA sample can be obtained from blood or sperm cells collected when taking semen samples for cryopreservation.
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From page 87... ...
Cryopreservation now offers a cost-effective way to retain a sample of the genetic diversity of a population of animals in suspended animation for indefinite periods of time. Current technology permits the cryopreservation of semen for A technician in a Brazilian laboratory tests a catheter before attempting embryo collection from endangered horses in Brazil.
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From page 88... ...
For special applications with these animals, however, cryopreservation of sperm is feasible. For REPRODUCTIVE AND MOLECULAR TECHNOLOGIES PRESENT CONCERNS AND OPPORTUNITIES FOR CONSERVATION Concern about conserving genetic diversity in livestock species is largely a response to technological innovations that have allowed widespread dissemination of genetic material from a limited number of highly selected breeds and individuals.
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From page 89... ...
The availability of frozen embryos removes this constraint, These twins were the third set of their type produced at the International Laboratory for Research on Animal Diseases using embryo transfer technology. A trypanotolerant N'Dama embryo and a trypanosensitive Boran embryo were implanted at the same time into this recipient Boran cow to produce hematopoietic chimeric twins.
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From page 90... ...
Recognition of the need to conserve genetic diversity must become an integral part of genetic improvement programs. The livestock breeder and molecular geneticist must be free to continue to attempt to maximize rates of improvement in livestock species, secure in the knowledge that the same technologies that facilitate improvement efforts can also aid in securing the levels of genetic diversity required to meet unforeseen future needs.
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From page 91... ...
and early hatched stages, but pregnancy rates are very low (Hayashi et al., 1989~. Three mouse embryo banks have been established for preserving defined inbred and mutant strains of laboratory mice (National Institutes of Health, Bethesda, Maryland; Jackson Laboratories, Bar Harbor, Maine; and Medical Research Council Laboratories, Carshalton, England)
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From page 92... ...
Survival of split embryos is further reduced after freezing, so splitting may not be an advantage in preservation. Embryos derived from the splitting of an original founder embryo may themselves be split to produce additional identical descendants, but the survival rate of the resulting embryos is markedly reduced.
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From page 93... ...
Survival rates are still low, however, and the process has only been done through three generations. For conservation it is important to retain as much genetic diversity as possible, which is accomplished by storing unrelated genotypes.
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From page 94... ...
Thus, the exchange of improved genetic stocks across countries has been expensive and often restricted in the past. Improved methods of disease detection and control and the use of frozen semen and embryos make international exchange of improved genetic stocks increasingly feasible.
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From page 95... ...
Research on technologies that could benefit preservation and use of animal genetic resources should be continued and expanded. New ideas, research results, and techniques are continuously being reported that can affect the methods and value of conservation.
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From page 96... ...
A DNA bank could ensure sufficient genetic material for molecular characterization of the specific genes and DNA segments of a population, inexpensively stored, which could provide researchers with the material for molecular biological and gene mapping studies of that population. Although DNA stores may aid evaluation and use of germplasm, they should not be considered presently viable methods for conserving the genetic resources of livestock.
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