CMMB 403 tutorial 2 test with comlete solutions

CMMB 403 tutorial 2 test with comlete solutions what is each abdominal segment on the ventral side of the larva characterized by? - answeranterior denticles (which point posteriorly) posterior naked region What did Christiane Nusslein-Volhard and Eric Wieschaus do? - answerscreened thousands of embryos for patterning defects to identify all the genes involved in the segmentation process what made Christiane Nusslein-Volhard and Eric Wieschaus research different from others who sought to research the segmentation process in flies? - answerthey looked at embryos whereas everyone else was looking at adult flies What was the methodology behind identifying the segmentation process and find what genes are involved? - answerforward genetics what is forward genetics? - answeridentifying genes/genotype that is responsible for a particular phenotype what are the steps of forward genetics? - answer1. treat adult male flies with a mutagen to generate independent mutations in their gametes 2. mutagenized males are crossed to WT females to produce many heterozygotes with independent mutations (F1) 3. breed independent heterozygotes to WT flies to produce more heterozygotes with the same mutation 4. breed heterozygotes together to produce homozygotes 5. screen mutants for abnormal phenotypes what mutagen was used in the forward genetics experiment? - answerethyl methanesulfonate (EMS) what were the results of the forward genetic screen? (aka characteristics of the hedgehog mutant?) - answer- same number of segments - naked region in each segment deleted - denticles duplicated in a mirror image (posterior segment lost) what kind of gene is the hedgehog protein classified as? - answersegment polarity gene what is the hedgehog bands called in a normal larva? - answerdenticle bands what is the hedgehog bands called in a hedgehog mutant larva? - answerdenticle lawn what experiment happened in 1992? - answer- drosophila hedgehog was cloned by 4 independent groups - the sequenced gene could now be used to make a PROBE to analyze gene expression what were the 3 different papers that were published about hedgehog homologs and who published them? - answer1. mouse homolog (DHH) - Andrew McMahon 2. chicken homolog (SHH) - Cliff Tabin 3. fish homolog - Phil Ingham what is an ortholog? example? - answerspeciation event (functional/sequence divergence) ex. SHH in mouse and chicken what is a paralog? example? - answerduplication event (functional/sequence divergence) ex. SHH, DHH, IHH what is a homolog? - answerumbrella term for both an ortholog and homolog what was the first vertebrate hedgehog gene? in what organism? - answerdesert hedgehog in mice what are the 3 types of mammalian hedgehog genes discovered? - answersonic hedgehog indian hedgehog desert hedgehog how did the DHH discovery in mice happen? - answersince hedgehog homologs in vertebrates would share sequence ho