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Developmental Genetics.pdf

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Western University
Biology 2581B
Jim Karagiannis

Developmental Genetics • Developmental Genetics => Transforming info stored in linear DNA => into 3D organism. • Characteristics of animal development: o Multi-cellular characteristic o Differentiation of cells => carry out a different function § Single celled zygote => decisions => complex multicellular organism w/ specialized & differentiated cells. • Determination: predetermines cell’s fate o Mechanism involved in regulating the choice of developmental fate a cell will eventually go into o Normal cells => turns into a migratory cell => determination-changed cell's fate from stationary to migratory o Determination does not execute process of causing cell to differentiate yet => all it does is predetermine what the cell will eventually become. • Differentiation: executes cell’s fate o Mechanism to bring about decided fate made by determination mechanism. o Differentiation turns stationary cells into a migratory cell. o Ex. Segmentation in fly => cells all look the same => but each cell already knows its fate & what it will differentiate into => determination causes cells to know their fate => once cells differentiate into a specialized cell => process of differentiation => cells know a lot about their fate early on in development. o THM: cells exhibit differentiation due to differential gene expression , which causes them to turn into specialized cells. o Give rise to pattern of expression => if genes show gaps or if the genes are showing a pair-rule pattern => pre-pattern of future segmentation => or how the segmentation would look like. • Gene expression: o Cells w/ exactly the same DNA genotype => exhibit distinct phenotypes from each other => via differential gene regulation & gene expression. o Development => all about differential expression of genetic informa tion => development is a problem of gene expression. o Developmental information is passed along a developmental pathway => coordinated system. • Levels of gene expression: o DNA => primary mRNA => mature mRNA => inactive protein => active protein § DNA => primary mRNA via txn § Primary mRNA => mature mRNA via splicing § Mature mRNA => inactive protein via tsn § Inactive protein => active protein via protein modification & mutations. • Four examples of loss of negative control: o LacZ gene => gf allele (Oc MT) => level of regulation @ txn o Transformer gene => gf allele (ms-site) => level of regulation @ splicing o Hunchback gene => gf allele (NRE) => level of regulation @ translation o RAS => gf allele (GTPase) => level of regulation @ protein modification • Regulation of splicing during drosophila sex determination: o Transformer gene is regulated @ level of splicing => male & female mRNA are distinct from one another => spliced differently . o Sxl protein is only present in females => Sxl protein binds to ORF of primary mRNA & blocks splicing machinery from splicing out intron 2 => full length ORF is present (nothing spliced out) => functional Tra protein => maintains female sex. o Males do not produce Sxl protein => nothing to block splicin g site => splicing occurs but
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