This document discusses different types of DNA markers that can be used for genetic mapping, including Restriction Fragment Length Polymorphisms (RFLP), Randomly Amplified Polymorphic DNA (RAPD), microsatellites, single nucleotide polymorphisms (SNPs), amplified fragment length polymorphism (AFLP), and isozymes. DNA marker testing determines which genetic variants or alleles an animal carries for traits like disease resistance, coat color, and horned status. While simple traits are controlled by a single gene, economically important complex traits are influenced by many genes and the environment.

1. DNA MARKERS FOR GENETIC MAPPING BLS 308 HOZA, A.S

4. Such traits - controlled by a single gene and a marker allele associated with that gene can perfectly predict the phenotype of that trait (the physical attributes of an animal).

5. DNA tests for simple traits include those for certain diseases:

6. DUMPS (Deficiency of UridineMonophosphateSynthase)

7. BLAD (Bovine Leukocyte Adhesion Deficiency)

8. coat color, and

10. Controlled by many genes

11. Influenced by the environment.

12. Examples of complex traits :

13. growth traits,

14. carcass characteristics and

15. reproductive performance.

19. RFLP markers have several advantages They are codominant and unaffected by the environment. 2) Any source DNA can be used for the analysis. 3) Many markers can be mapped in a population that is not stressed by the effects of phenotypic mutations.

20. Variations occurring within a species in the length of DNA fragments generated by a specific endonuclease.

28. Example, alleles of malicdehydrogenasewould both perform the correct enzymatic function, but the electrophoretic mobility of the two may differ.

30. The extracts are next separated by electrophoresis in a starch gel.

31. The gel is then placed in a solution that contains reagents required for the enzymatic activity of the enzyme you are monitoring.

32. In addition, the solution contains a dye that the enzyme can catalyze into a color reagent that stains the protein.

34. To date, only 40-50 reagent systems have been developed that permit the staining of a particular protein in a starch.

35. Not all of these reagent systems work efficiently with all plant species. Therefore, for many species only 15-20 loci can be mapped.

36. A second drawback is tissue variability.

37. Some isozymes are better expressed in certain tissues such as roots, whereas other are best sampled in leaf tissue.

38. Therefore, several samplings of the segregating population are necessary to score all the available isozyme.

39. Because neither of these drawbacks affect RFLP or RAPD loci, isozyme loci are rarely scored today.