BIO 326 Lecture Notes - Lecture 6: Palaeoptera, Ontogeny, Hemimetabolism
20 Dec 2017
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Growth vs. development: growth: increase in organism"s mass, length, etc. over time, development: change in stage over time. Molecular insights into development: most of our understanding of insect development comes from examining drosophila mutations, early development is controlled by a hierarchy of transcription factors. Proteins that bind to dna, acting as an on/off switch for production of specific proteins: we will go through the most important zygotic segmentation genes regulated by the transcription factors throughout embryonic development now. Maternal effects genes: from maternally inherited mrna migrate to poles of embryo. Gap genes: divide the embryo into broad, slightly-overlapping zones from anterior to posterior. Pair rule genes: determine the number of segments in the embryo. Homeotic genes: determine the identity of segments (e. g. , head, thoracic, abdominal) as shown previously. Seen in palaeoptera and some neoptera: endopterygote or holometabolous development wing rudiments are absent in immatures and develop from internal structures called imaginal discs, with reorganization of body during pupal stage.
