Introduction

Objectives

Participants

Microsatellite panel

Standard DNAs

ISAG/project comparison

Blood typing

DNA Typing

Links

Project Database

Projects

Roslin Institute

 

Cattle Diversity by DNA Typing

There are now a few minisatellite probes and several hundred microsatellite markers available that cover the bovine genome that have been produced as part of the Bovine genome mapping project.

Work with microsatellite markers has shown that they are valuable tools for examining genetic diversity and phylogeny in many species.

All markers, whether selected to cover the genome or to mark trait loci, are PCR-based. They are, for the most part, microsatellite loci, although some specific genes are PCR-RFLP markers. For the microsatellite loci, four techniques are used for genotyping depending on the facilities available to the participating laboratories.
These techniques are:

• Manual determination of alleles using denaturing gel electrophoresis with PCR products visualised by silver staining.
• Manual determination of alleles using denaturing gel electrophoresis with radioactively labelled PCR products visualised by autoradiography.
• Use of Pharmacia ALF automated genotyping equipment using adjacent sizing standard.
• Use of ABI373 automated genotyping equipment with internal sizing standard.

In order to provide sufficient DNA for analysis, distribution amongst laboratories and to establish a DNA bank from which samples can be distributed, DNA is prepared from 10mls of blood. To ensure long term stability of the DNA, an extensive protocol using proteinase digestion and phenol extraction is used, rather than the brief salt precipitation methods.

For work carried out in different laboratories to be comparable, it is essential that the same markers and typing protocols are used. Specifically, thirty microsatellite markers have been agreed for use across Europe.

Previous experience has shown that results are variable depending on the method used and the laboratory involved. In general, the methods give standard errors so that a correction factor can be applied to standardise results for comparison.

All samples from all breeds are genotyped for all markers selected, including the trait markers irrespective of the type of breed,
e.g. beef breeds will also be typed for markers affecting milk traits.
Results are expressed as an allele number and results for all individuals in a breed are reported to the project database.

If you would like to register for the cattle diversity database, please contact Geraldine Russell.
Access the database if you have already registered.