Lecture 18

One module can change while another remains the same 2

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Unformatted text preview: in different vertebrates: Nieuwkoop center and Spemann ­Mangold organizer Homologs of the same genes used in all organisms Modularity: Development occurs through a series of discrete and interacCng modules The eye and the limb are not connected in their development. One module can change while another remains the same 2 4/11/13 Modularity: perhaps early events are so conserved because they have to be (or the embryo will die) Organ structure differences and similari=es can be seen rela=vely early in embryonic development Limb field size differences between two winged animals: bat and kiwi What about structures that develop LATER: ie, the eye, the limb, the other organs? Development of (A) the bat which has a large forelimb bud and wing, and the (B) kiwi, a flightless bird with relaCvely small forelimbs (aAer Richardson 1999). But iniCal padern of cells that will make different bones is the same. All these wings are homologous structures A juvenile s=ckleback head stained red for developing bone and blue for forming car=lage. Descent with modificaCon (2010) PLoS GeneCcs Issue Image | Vol. 6(2) February 2010. PLoS Genet 6(2): ev06.i02. doi:10.1371/image.pgen.v06.i02 hdp://www.plosgeneCcs.org/arCcle/info:doi/10.1371/image.pgen.v06.i02 Modularity in DNA sequences The sCckleback (a fish) Marine Freshwater How does smaller ­scale change occur within the same species? Pitx1 gene Pitx1 expression pattern (pitx1 mRNA=blue color) Arrows point to nose and jaw in c Pelvic region in d 1. IdenCfy genes that are involved in producCon of pelvic spines 2. Are there changes in this gene when you look at sCcklebacks that look different? What is a possible explanaCon for the different expression paderns of pitx1 in these two fish? a. Freshwater sCcklebacks have a mutaCon in the coding region of Pitx1 b. Freshwater sCcklebacks have a mutaCon in the 3’UTR of Pitx1 c....
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