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Lecture 20

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Human Biology
Stephen Wright

HMB265 - Lecture 20 Model organisms - why are they chosen? Easy to grow in lab Rapidly reproduce Small size Large collections of mutants with developmental defects maintained in stock centers Genes and pathways are conserved Genomes sequenced Easier for geneticists to identify genes with mutant phenotypes How relevant is the information gain from drosophila to understanding human development when there is a giant evolutionary difference? Alot of genes and basic strategies of development are conserved across multi-cellular eukaryotes Commonalities found across very different species Pax-6 andAniridia wild-type genes can direct eye development in drosophila (these genes are found in humans) These genes can be knocked out in drosophila and replaced with the human alleles, saving the phenotype. This is very surprising given the difference in morphology and evolution between drosophila flies and humans An individual with 1 defective copy ofAniridia have defects in the iris - can cause reduction in sharpness of vision, and cause greater sensitivity to light. It is an autosomal dominant condition. The homozygous condition is lethal and cause Once you have knocked out the gene, you can observe the phenotype and make conclusions on development based on the observations you make. In the opposite direction, you can expose a mouse to a mutagen and screen the progeny (at the level of the phenotype) for differences and identify a mutated gene These techniques are not restricted to studying development, but they are very successful for this process. Drosophila have been important in understanding the basic body plan in animals. One of the huge advantages of studying an invertebrate is the ease of identifying developmental mutants due to the clear exoskeleton. Used a novel screen to identify different genes that The screen divided maternal genes and zygotic genes. Maternally required genes are expressed in the egg before the Mutations in these genes display a mutant phenotype in the Zygotic genes Classes of drosophila segmentation gene mutants Gap mutation
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