bicd130_06_lecture17r - BICD 130 Embryos, Genes, and...

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Unformatted text preview: BICD 130 Embryos, Genes, and Development Germ plasm and chromosome diminution in Parascaris (nematode worm) Boveri s spindle reorientation experiment Inheritance of germ plasm confers chromosome retention Pole cells in Drosophila are the germ line precursors Pole cells Drosophila polar granules germ cell-less (gcl) mRNA is a component of Drosophila germ plasm The Gcl protein participates in transcriptional silencing of germline precursor cells Certain posterior group genes are essential for both abdomen and germ plasm formation in Drosophila Posterior group genes required for pole cell formation in Drosophila oskar tudor vasa valois (nanos is required for pole cell migration and subsequent germ cell development) Anterior localization of oskar mRNA results in the formation of ectopic pole cells ' Drosophila germ cells are carried interiorly by the posterior midgut invagination Germ cells Primordial germ cell migration in Drosophila Primordial germ cell migration and coalescence with gonadal mesoderm in Drosophila tin Cystoblast network and oocyte choice in Drosophila The fusome is a membrane-associated cytoskeletal organelle rich in the protein spectrin The cell (1) that retains more of the fusome during the first division becomes the oocyte The meroistic ovary of Drosophila actin ring canals actin DNA (Contrast with panoistic: no nurse cells; oocyte supplies own macromolecules) P granules mark the germ line lineage of C. elegans DNA P granules P granules are segregated to the posterior daughters of early cell divisions in the C. elegans embryo Transcriptional silencing of germline precursor cells in C. elegans P2 mRNA from pes-10-lacZ reporter gene Sequential gametogenesis in C. elegans hermaphrodites Activation of the Notch pathway by a signal from the distal tip cell promotes germline mitosis Lag-2 ligand Glp-1 receptor The spermatogenesis-oogenesis switch in C. elegans hermaphrodites Translational repression by Drosophila Nanos Xenopus germ plasm becomes localized to the blastocoel floor Xcat2 mRNA in Xenopus vegetal cortex Xcat2 is the Xenopus homolog of nanos Germ cells in vertebrates must migrate to the genital ridge The germinal crescent of birds and reptiles contains the PGCs Primitive streak Epiblast Staining: chick Vasa homolog Primordial germ cells of birds and reptiles migrate to the gonads via the blood vessels PGCs (arrowheads) PGC migration in amphibians and mammals is via the gut PGCs reside initially in the posterior epiblast and enter the hindgut endoderm at the start of their migration Germ cells associate intimately with gonadal cells Germ cells associate intimately with gonadal cells DNA Oct4 Inner cell mass Oct4-lacZ reporter gene Oct4 antibody (ovary) Oct4 antibody (testis) Oct4 is a marker of totipotent germ cells in the mouse ...
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