Discuss how the advent of recombinant DNA technology improved upon historical genetics research ...

Mutations play a central role in genetics. Historically, transmission of mutant alleles from generation to generation was studied to discover the basic principles of genetics. In addition, geneticists used induced and spontaneous mutations in laboratory organisms to dissect biological processes such as metabolism, cell structure, and development. Gradually, mutational analysis became the method of choice for establishing how many genes are contained in an organism's genome. While this approach worked well for experimental organisms, human genetics grew very slowly because of its reliance on indirect and inferential methods for collecting and analyzing information about the inheritance of genes in our species. Although analysis of mutants is a useful tool in genetics, the other side of mutations is that they are responsible for many inherited disorders in humans. If we hope to learn how many genetic disorders humans can have and how to develop treatments for those diseases, we need to know how many genes are in our genome, know where they are located on our chromosomes, and have ways of establishing their functions. Genetic mapping is one step to accomplish these goals. In human genetics, this approach began in the 1930s, when Julia Bell and J. B. S. Haldane used pedigree analysis to show that the genes for hemophilia (MIM 306700) and color blindness are both on the X chromosome.
Beginning in 1980, geneticists began mapping DNA sequences to specific human chromosomes. Most often, those sequences weren't genes but simply markers that detected differences in restriction-enzyme cutting sites or differences in the number of repeated DNA sequences in a cluster. However, once these markers were assigned to chromosomes, they became valuable tools in linkage studies.