Segmentation of genomes

The PCR (Fig. 10) allows small segments of genomic DNA removed from crude cell lysates to be amplified in quantities sufficient for subsequent analysis. This is achieved by using a succession of incubation steps at different temperatures. Fundamental to the procedure are a pair of oligonucleotides, or primers, that are made synthetically with nucleotide sequences complementary to those of the 3 and 5 ends of the gene segment of interest. One primer corresponds to the 3 end and one to the 5 end. The DNA sample is first heated to 94°C to convert it from... 

Genetic recombination arises by exchange of homologous segments of DNA between viral genomes, most often during the replication process. The enzymes involved in recombination are DNA polymerases, endonucleases, and ligases, which also play a role in DNA repair and synthesis processes. 

Recombination will occur more frequently the greater the number of nucleotides that separate the marker from the mutation. Some segments of the genome, "hot spots," are more prone to recombination than others (Goldstein, 2001). 

From the Human Genome Project, we know that there are approximately three billion base pairs that make up the DNA molecule (refer to Appendix 2). Only certain segments of the enormous DNA molecule encode for proteins. These segments are called genes. The estimate is that there are about 30,000 genes that encode proteins. Exhibit 2.1 provides some information about the number of genes and the complexity of life forms. 

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