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12: Tracing Origins

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    • 12.1: Introduction
      What constitutes being human? Many will point at cultural identity and leaving long-standing remnants of that culture. Such prehistorical artifacts like cave drawings and tools provide an anthropological framework for identifying what it is to be human, but the biological identity remains locked in the history of our DNA. Homo sapiens represent a branch of primates in the line of Great Apes. The family of Great Apes consists of four extant genera: Homo, Pan, Gorilla, Pongo.
    • 12.2: Maternal Lineage
      Mitochondria are thought to have arisen in the eukaryotic line when bacteria capable of detoxifying the deadly effects of atmospheric oxygen were engulfed by a eukaryote that did not proceed to consume it. Over time, these formerly free-living bacteria became dependent on the eukaryotic cell environment while providing the benefit to the host cell of aerobic respiration. Mitochondria still replicate independently of the host cell but can not survive outside of this cellular environment.
    • 12.3: Maternal Lineage (Activity)
      There are 2 hypervariable regions within the control region of the mitochondria. This exercise amplifies just one of these. For more definitive results, both should be amplified and sequenced. This exercise will permit us to have a rough idea of the origins of our maternal line and we will be able to attribute ourselves to various tribes throughout the world. The human mitochondrial genome (genbank file).
    • 12.4: Alu Insertion (Activity)
      Alu’s are unique SINEs that appear in the primate lineage and reveal the lineage and diversification of primates. While retrotransposons can disrupt gene (as in some cases of hemophilia), they often land outside of genes or within introns without effect. One example of a non-disruptive Alu element in humans is found in the location called PV92 on chromosome 16. This element is of the youngest subfamily of Alu, called Ya5.
    • 12.5: Transposons
      Mobile genetic elements called transposable elements or transposons are located throughout the genome. These elements were first described in maize by Barbara McClintock at the Cold Spring Harbor Laboratory where she observed a disruption of coloring in corn kernels that did not follow simple Mendelian inheritance. Dr. McClintock noticed that some kernels contained spots. She described the phenomenon of this break in the Mendelian characteristics as a “genetic instability”.

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