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Lecture 16

Biology 1002B lecture 16

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Biology 1002B
Tom Haffie

Lecture 16 ????likelihood that modern multi-cellular life forms are monophyletic. - 50/50 - life is not monophyletic for multi-cellularity. ??????characteristics of Volvocine algae that make them a useful model system for studying the transition to multi-cellularity. - Volvos is not monophyletic relative structure/function of Chlamydomonas vs. Volvox cells. - Chlamy: oval, unicellular, mobile cells - Volvox: two kinds of cells, thousands of these small somatic cells that still have flagella, eyeyspots and only a dozen of these gonidial cells (larger) that are on the inside. o More extreme partitioning of cells o ECM (extra cellular matrix) is holding this sphere together general process of Volvox asexual reproduction; role of somatic vs gonidial cells. - Some cells are larger than others, there is an asymmetric division - The larger cells will become gonidia (reproductive cells) - The smaller cells will become somatic cells and wont reproduce - End up with tons of somatic cells with large gonidial cells on outside - There is a crack, the reason for this crack is because all the cells are inside out so they use the crack to flip themselves inside out so now flagella and eyespot is pinting out and gonidial (reproductive cells) are on the inside. Now this organism can respond to light, it is phototrophic. - Somatic cells that are not on the outside are going to die. genetic approaches to identifying genes relevant in rise/maintenance of multi-cellularity. - maybe treat volvox with a mutagen, make mutagen baby volvoxes and find the ones that are messed, the ones that cant do inversion or cant stick together so we can find effective mutants and see which genes are effected. - Could compare the genome of clammy and volvox. - Look in somatic and gonidial cells and see the regulation of genes in those two kinds of tissues types of data or insight revealed by comparative genomic studies in Chlamydomonas vs. Volvox - genome sizes are not much different - protein coding genes, almost identical, they have about the same number of protein coding capacity. types of data or insight revealed by mutation/rescue experiments in Volvox. - GLS, gene that is responsible for the asymmetric division, such that if its mutated, the cells end up being the same size and we don’t get the gonidia that we expect. - If everything goes correctly, then in the la
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