CONSERVATION OF ARABIAN GAZELLES - Nwrc.gov.sa

8. Use of DNA-based Methods in Mammalian Taxonomy
and Population Genetics
Eric H. Harley, M. Faadiel Essop, Colleen O'Ryan,
Nomusa Mda and Derek Ohland
Abstract: Examples of the lise of three different methods of DNA analysis are given to illustrate
their relative value in providing answers to questions of phylogenetic relationships as well as
questions at the population genetic level. and to show how some of these can be of direct relevance to
practical problems of conservation management. Restriction Fragment LengTh Polymorphism
(RFLP), restriction mapping, and direct deoxyribonucleic acid (DNA ) sequen cing approaches are
compared, with examples from studies Oil rhinoceros, antelopes. elephant. dolphins. and birds.
Keywords: DNA analysis, taxonomy,. population genetics, conservation.
Introduction
Deoxyribonucleic acid (DNA)-based methods can be used to address many interesting aspects of
systematics or population genetics in animals, plants, and micro-organisms, so me with direct
conservation relevance. There are a number of different approaches which can be used to implement
such studies, and an outline of these approaches, and their reliability, has been discussed previously
in these Proceedings (Harley and Vassart, Article 6). In this article some examples of the uses of
these methods will be presented to illustrate the sort of problems which can be addressed by each of
the different approaches.
Before DNA studies can be undertaken, it is necessary to obtain the appropriate tissue sample
from which to extract the DNA, and to decide whether the problem is best solved using nuclear or
mitochondrial DNA. In mammals, mitochondrial DNA evolves about five to ten times as fast as
nuclear DNA. and has a number of properties (Harley and Vassart, Article 6) useful for studies which
have conservation relevance, and the examples to be described will therefore concentrate on the use
of mitochondrial DNA. This presents the investigator with a practical problem, since studies using
the Restriction Fragment Length Polymorphism (RFLP) or restriction mapping approach are most
easily performed using purified mitochondrial DNA. Unfortunately, such studi es require significant
quantities (between five and 100 g) of fresh tissue, usually heart muscle, skeletal muscle, or li ver,
which except in the case of the largest animals can only be obtained postmortem. However, the
RFLP and to a lesser extent the mapping approach can be used on smaller samples requiring less
in vasive sampling procedures (blood, Or cell cultures made from skin biopsies) but the more
laborious Southern blotting laboratory approach is then required for analysis of the DNA.
Fortunately the most powerful and versatile approach, DNA sequencing, poses the least problematic
sa mpling problem, since almost any tissue sample is adequate. Unfortunately. the culture of cells
remains an expensive technique.
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