APPROACHES AND CHALLENGES IN MEASURING GENETIC DIVERSITY IN PIGS (AVANCES Y RETOS EN LA MEDICIÓN DE LA DIVERSIDAD GENÉTICA EN LOS CERDOS)

Rothschild M.F.

Description

Abstract
While the number of diverse genetic breeds of pigs may exceed 600 worldwide, there is a limited amount of information to assess their genetic and functional diversity. Efforts have primarily been conducted to examine genetic diversity using anonymous markers and to a more limited extent individual gene markers and mtDNA. This paper discusses the methods used to date and the need to examine other methods to more fully understand not only the genetic diversity but the functional diversity of different pig breeds.
Resumen
Aunque el número de razas genéticas de cerdos distintas excede de las 600 en todo el mundo, hay una disposición limitada de información para acceder al conocimiento de su diversidad genética y funcional. Los esfuerzos deben ir preliminarmente conducidos a examinar la diversidad genética utilizando marcadores anónimos y con una extensión más limitada a marcadores génicos individuales y ADNmt. Este trabajo discute los métodos utilizados hasta la fecha y la necesidad de examinar otros métodos para un conocimiento más profundo no sólo la de la diversidad genética, sino la diversidad funcional de las distintas razas porcinas.

Sujets

• Pig
• Genetic diversity
• Functional diversity
• Gênes
• Cerdo
• Biodiversidad

Informations

• Publié par: erevistas
• Publié le: 01 janvier 2003
• Nombre de lectures: 9
• Langue: English

Extrait

APPROACHES AND CHALLENGES IN MEASURING GENETIC
1DIVERSITY IN PIGS
AVANCES Y RETOS EN LA MEDICIÓN DE LA DIVERSIDAD GENÉTICA EN LOS CERDOS
Rothschild, M.F.
Department of Animal Science. 2255 Kildee Hall. Iowa State University. Ames, Iowa 50011. USA.
ADDITIONAL KEYWORDS PALABRAS CLAVE ADICIONALES
Pig. Breeds. Genetic diversity. Functional diver Cerdo. Razas. Diversidad genética. Diversidad
sity. Genes. funcional. Genes.
SUMMARY RESUMEN
While the number of diverse genetic breeds Aunque el número de razas genéticas de
of pigs may exceed 600 worldwide, there is a cerdos distintas excede de las 600 en todo el
limited amount of information to assess their mundo, hay una disposición limitada de informa
genetic and functional diversity. Efforts have ción para acceder al conocimiento de su diver
primarily been conducted to examine genetic sidad genética y funcional. Los esfuerzos deben
diversity using anonymous markers and to a ir preliminarmente conducidos a examinar la di
more limited extent individual gene markers and versidad genética utilizando marcadores anóni
mtDNA. This paper discusses the methods used mos y con una extensión más limitada a marca
to date and the need to examine other methods dores génicos individuales y ADNmt. Este trabajo
to more fully understand not only the genetic discute los métodos utilizados hasta la fecha y la
diversity but the functional diversity of different necesidad de examinar otros métodos para un
pig breeds. conocimiento más profundo no sólo la de la
diversidad genética, sino la diversidad funcional
de las distintas razas porcinas.
1Presented at Symposium on Pig Biodiversity,
Córdoba, Spain November 7 10, 2002. This is a
INTRODUCTIONjournal paper of the Iowa Agriculture and Home
Economics Experiment Station, Ames, Iowa,
Project No. 3609, and was supported in part by The pig was one of the first animals
Hatch Act and State of Iowa funds and funding
likely to have been domesticated over
from NRSP 8 and the USDA/CSREES Pig Genome
5,000 years ago (Rothschild andCoordination program. The author gratefully
acknowledges input received from Graham Ruvinsky, 1998). To date there are
Plastow, Louis Ollivier and Juan Vicente Delga likely over 600 breeds or lines
do. By no means will this be an exhaustive review
worldwide of which the most reside in
of the literature but it will touch on issues central
China and Europe and over 200 areto livestock. The author apologizes for references
of work that he has failed to cite. considered endangered (Ollivier et al .,
Arch. Zootec. 52: 129 135. 2003.ROTHSCHILD
2001). Considerable differences appear diversity should be used to help in the
to exist both morphologically and determination of breed differences and
physiologically between the various in determining those which must be
domestic breeds and their wild boar preserved.
ancestors from Europe and Asia The objectives of this paper are to
(Giuffra et al., 2000). These changes review in general terms ways to
in the domestic pig have reflected the measure genetic diversity among and
rather plastic nature of the pig and within pig breeds and to discuss
humankind's ability to genetically methods to quantify diversity and rela
manipulate it to fit certain needs and te it to functional importance.
markets.
A large percentage of pig breeds
METHODS TO DETERMINE GENETICare now in danger of extinction and
DIVERSITYothers are threatened by inefficient
use and loss due to crossbreeding.
Over the past ten years considera Efforts to determine the level of such
ble improvements in molecular geneticsrisk are underway, especially in Europe
have led to the development of geneticbut also in other parts of the world. In
maps of many organisms. TheseEurope, at the European Association
advances in molecular biology havefor Animal Production, an Animal
made it possible to develop compre Genetic Data Bank has been establis
hensive genetic linkage maps in the pighed as a repository to record such
(e.g. Archibald et al., 1995; Rohrer etbreeds and to assess risk (see Simianer
al., 1994; 1996). To date, over 6,000and Meyer, 2003, in this Proceedings).
genes and anonymous markers haveAlong with assessment of risk is the
been added to the gene map of the pigconsideration of which breeds should
(see www.thearkdb.org or http://be preserved. Certainly there is the
iowa.thearkdb.org)increased interest in this approach and
In addition to identifying andthere is some support by private
mapping genes and markers, animalorganizations and governmental
geneticists have begun to search forprograms. Ruane (1999) has provided
the individual genes that affect traits ofa set of criteria to be considered when
interest in the pig. Since the earliestchoosing a specific breed for a con
quantitative trait loci (QTL) scan inservation program. The degree of
pigs by Andersson et al. (1994) manyendangerment and genetic uniqueness
others have followed and a number ofof the breed are two of seven essential
criteria discussed. However, while regions are now identified (see review
breeds have cultural and historical by Bidanel and Rothschild, 2002). In
value, from an economic point of view,addition, the candidate gene approach
the functional diversity for a set of (Rothschild and Soller, 1997) has been
important economic traits should be employed and many candidate genes
considered the most important criterion. have been shown to be associated with
Efforts therefore to determine both traits of interest (Rothschild and
genetic diversity and functional Plastow, 1999). These QTL and
Archivos de zootecnia vol. 52, núm. 198, p. 130.MEASURING PIG GENETIC DIVERSITY
candidate genes form the basis of A number of genetic methods exist
comparison of genetics related to to measure genetic diversity. These
functional differences. include comparison of anonymous
Key issues to discuss include but markers such as microsatellites,
are not limited to 1) What is genetic minisatellites, and amplified fragment
homology/diversity? 2) How is it best length polymorphisms (AFLPs), gene
measured? 3) What is functional markers/SNPs (single nucleotide
diversity and how is it best assessed? polymorphisms), large scale or directed
Some examination of what has occurred sequencing, mitochondrial genotyping,
in other fields may be useful for and Y chromosome genotyping. Mini
discussion purposes. Evolutionists are satellites are the preferred method in
interested in knowing if two species human studies and allow for seeing
are related. Therefore, interest is in expansion and hence direction of
evolutionary changes and knowing that evolution. Mitochondrial (mtDNA)
the genes are the same is not enough. genotyping has also been used to look
Given two DNA sequences, a resear for different female lineages and Y
cher can ask the question: How much chromosome genotyping has also been
evolutionary change has occurred used for measuring ethnic differences.
between these two sequences? Dealing with only 2 narrow genomic
Seemingly this appears to be a simple regions, Y and mtDNA, give some
question but the answer may prove insight into possible phylogenetic
elusive. Researchers can use observed origins, among the many others that
differences and the simplest measure SNPs in autosomal regions might
of distance is to count the number of indicate.
nucleotides that differ between the In livestock early measures of
two sequences. This approach has been diversity were associated with protein
used in livestock (Giuffra et al ., 2000; polymorphisms measured on 2D gels.
Kijas and Andersson, 2001) to exami More recently, several recommen
ne evolutionary changes in the pig. dations have been made for genetic
However, there are potential problems diversity studies (Barker et al ., 1998).
with such an approach because if These recommendations include use
change has been common then the of 2 5 microsatellites per chromosome
same site may have undergone repeated and genotyping of 50 animals (25 of
substitution. So as more time passes, each sex) that are unrelated. Breeds
the number of differences between that differ in the frequency of alleles at
two sequences becomes a less accuratethese loci are declared different or
estimate of the actual number of diverse after determination of genetic
substitutions that truly occurred. As a relationships or genetic distances
general rule animal geneticists and between breeds (Barker et al., 1998).
breeders have a different problem in Examples of these approaches include
that they are not only interested in an European Community project that
homology but also genetic and functio was recently completed to evaluate
nal diversity, even so the same types of the genetic diversity of European pig
concern exist relative to comparisons. resources (considering more than 50
Archivos de zootecnia vol. 52, núm. 198, p. 131.ROTHSCHILD
breeds) using primarily microsatellites considered were disease resistance,
and AFLP markers (Laval et al ., 2000; growth, coat color, meat quality and
San Cristobal et al ., 2002). For details prolificacy. Ciobanu et al . (2001) found
see http://databases.roslin.ac.uk/ significant differences in five of the
pigbiodiv. However, just as with ten characterized polymorphisms and
evol