Animals 3 - SEGMENTATION A key innovation Found in...

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1 Animals 3 SEGMENTATION •A key innovation • Found in arthropods, annelids, chordates, and misc. others • Blocking out of an embryo into regions where specific body parts will eventually develop • Segmentation determined early in development • Differential expression of HOX genes determines the exact location of appendages • HOX genes evolved before segmentation – made segmentation useful • Sponges have one HOX gene; Cnidarians have at least two Segmentation means having a body comprised of sequential elements called segments . Key innovation Homeotic genes •M a s t e r regulatory genes that direct development • After segmentation is established – these genes determine what kinds of appendages are produced on what segments • Fruit fly homeobox genes include a specific 180-nucleotide sequence (aka, a homeobox) • This sequence is extremely similar to that found in many other animals (such as birds,
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Animals 3 - SEGMENTATION A key innovation Found in...

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