Final answer:
Common DNA landmarks for mapping human genes include genetic markers, known genes or DNA sequences associated with traits, and physical markers, measurements of the actual distances in nucleotides between DNA sequences. Both are essential for building comprehensive genetic and physical maps of the genome.
Step-by-step explanation:
Two commonly used DNA landmarks for mapping human genes are genetic markers and physical markers. Genetic markers are genes or DNA sequences that have a known location on a chromosome and are associated with a particular trait or disease, making them useful for establishing linkage maps. Physical markers involve concrete measurements of the physical distances between genes or DNA sequences, measured in nucleotides, and are pivotal in creating physical maps of the genome. Both types of DNA landmarks are crucial for building a comprehensive picture of the human genome and facilitate the study of genetic disorders and the evolutionary relationships among species.