L62-07 Early Development-HANDOUT-6

L62-07 Early Development-HANDOUT-6 - Lecture 62 Animal...

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1 Lecture 62 Animal Development The study of development. .. Follows events from a single cell (zygote) to an adult (billions of cells) Focus is on questions about: 1. the morphology at different stages: (how do organs, limbs etc. arise) 2. the mechanisms of differentiation 3. the role of the genome in development Sequence of Events • Fertilization • Cleavage • Gastrulation • Organogenesis Gametes to zygote blastocoel gastrula, with blastopore, archenteron neurulation, organs and organ systems formation Major Trends 1) Increase in cell number 2) Increase in complexity and specialization. 3) How is it controlled? Information is carried in DNA, but how is its expression regulated? Sea urchin genome con f rms kinship to humans and other vertebrates • Genome of 814 megabases • 23,500 genes • Complex immune system • 11,500 genes turned on during f rst 2 days of development • An estimated 95% of 283 transcription factors were functioning before larval formation 48 hours embryo Purple sea urchin Strongylocentrotus purpuratus Source: Science 10 November 2006 Vol. 314 Sea urchin genome con f rms kinship to humans and other vertebrates • More than 900 genes designed to sense light and odors - similar to vertebrates • More complex innate immune defense than vertebrate’s • Has adaptive immune defense genes but not producing antibodies Light sensing proteins, yet not sensing light Pluteus larva Source: Science 10 November 2006 Vol. 314
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2 Events of Fertilization in Sea Urchin Acrosome membrane breaks Polymerization of actin f laments forms acrosomal process Enzymes released to digest jelly layer Acrosomal process binds to
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L62-07 Early Development-HANDOUT-6 - Lecture 62 Animal...

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