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A Word on This Activity Back to Build a Family Tree This game is a highly simplified example of the reasoning and type of analysis geneticists use to study Y-chromosome heredity. Geneticists look at many different types of polymorphisms, or known regions of genetic variation, that occur on the Y chromosome. In this interactivity, we use sequences that are only 20 base pairs long and show only one type of mutation known as a base substitution, in which one letter is substituted for another. Geneticists typically look at many other types of mutational differences, including insertions, deletions, duplications, and tandem repeat sequences along different regions of the Y chromosome. To compare multiple sequences that can be thousands of base pairs long, researchers use computer software packages, called computer matching and alignment systems, to measure the degree of similarity between chromosomes. In order to be able to visually match differences between DNA sequences in this game, we greatly exaggerate the mutational rate. Mutational rates along the Y chromosome are exceedingly low, so the amount of DNA difference between father and son is almost negligible. Although this game is a simplification, it provides a basic understanding of how geneticists use the Y chromosome for male-line genetic research, and how they can determine the relatedness of individuals and populations by looking at polymorphic regions on the Y chromosome. Back to Build a Family Tree Where are the Ten Lost Tribes? | Tudor Parfitt's Remarkable Journey Mystery of Great Zimbabwe | Build a Family Tree | Resources Teacher's Guide | Transcript | Site Map | Lost Tribes of Israel Home Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print PBS Online | NOVA Online | WGBH © | Updated November 2000 |