BIO 1305 Lecture Notes - Lecture 11: Hox Gene, Thyroid, Lancelet
16 Dec 2017
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Set the blueprint of where structures should be. Hox genes control the development of major regions of the vertebrae brain; they organize major regions of the forebrain, midbrain, and hindbrain. Vertebrates have 2 or more sets of hox genes; lancelets and tunicates have only one cluster. Mucus serves as protective measure (and possible health cure: lampreys tend to be parasitic. Mouth indicates it probably was a suspension feeder. It resembled a lancelet and also had characteristics of vertebrates. Organisms with extra hox genes have increased diversity, such as an enlarged forebrain associated with enhanced smell and vision. Males have a pair of claspers in their pelvic region that transfer sperm into female reproductive tract. Oviparous- laying eggs that hatch outside mother body. Ovoviviparous- retain fertilized egg in oviduct, nourished by egg yolk. Ray- and lobed- finned fishes have swim bladders which allow the fish to change their depth in the water.
