模式动物介绍.pptVIP

Redundancy in mammals is important here… easier to identify gene function in flies where only one copy is present. Redundant function in mammals makes it hard to identify function of single gene. In situ hybridization of vertebrate embryos shows expression of hox genes in similar pattern Start with Hox patterning then switch to gene complexes specific to organ or structure. Organ patterning determined by these complexes. Size and shape also studies…not cell number dependent..physical distance between cells at opposite ends of structure…still not understood but Drosophilia is a good model to use Also study genes resposible for terminal differientiation of a cell within a tissue * An Introduction to Model Organisms of Development Gas: 2000 liters of methane gas released/day! What makes a good model organism? Gas: 2000 liters of methane gas released/day! Size : 6 tons 250kg food eaten every 100kg of elephant dung/day Gestation : 23 months Females give birth to single offspring every five years Sexual maturity at age 12 What makes a good model organism? Size : 1 mm in length Live on a diet of bacteria Gestation : 500,000 offspring in 1 week from single organism Sexual maturity in 3 days Genome : Sequenced! Drosophila melanogaster Caenorhabditis elegans Arthropods Nematodes Xenopus laevis Amphibians Mammals Mus musculus Homo sapiens Caenorhabditis elegans Nematode Worm Nematodes account for an estimated four of every five animals in the world ! Smooth-skinned, unsegmented worms first used as a model organism by Sydney Brenner in 1965 C. elegans is diploid and has five pairs of autosomal chromosomes (named I, II, III, IV and V) and a pair of sex chromosomes (X). Most adults are hermaphrodite (XX) but .05% of lab populations are male (XO) Lifespan is 2 to 3 weeks Worms are usually kept on petri plates and fed E.coli About 10,000 worms fit on a single plate 959 Somatic cells - all visible with microscope - 300 neurons - 81 muscle cel