Just as we chart the world around us, we can map human chromosomes. The features of chromosomes can include protein-coding genes, ancient molecular parasites known as transposons, or stretches of repeat sequences. In this section, take a guided tour of less than 1% of your genetic material to see new and unusual views of your chromosomal landscape. (DNAi location: Genome > Tour > flyover > Intergenic regions and transposons)

Next we encounter two small genes that encode olfactory receptors, common features of Chromosome 11. These are followed by an "intergenic region" of 183,000 nucleotides, lacking any known genes. Scattered throughout this region are numerous "simple repeats" composed of multiple copies of a repeated sequence of 2-50 nucleotides. Two green blocks identify repeats longer than 100 nucleotides. Variations in the number of repeats between people, create a DNA difference, or "polymorphism," which can be used in forensic biology, paternity testing, or disease diagnosis. Blue and purple boxes identify the more than 100 transposons that litter the intergenic region. These molecular parasites make up about half of the human genome by weight, and the majority move about using an enzyme that was later borrowed by viruses such as HIV. Each of the millions of transposons in the human genome arose from an individual "jump" at some point in evolution. The majority of transposons have not jumped for millions of years and, thus, are "molecular fossils." As we will see, the majority of transposons are located within gene clusters and even within genes – a fact that perplexes scientists.

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