Mon Spr W2 - Genetic Analysis and Mutagenesis Screens (Lec1) Describe and explain how conditional mutagenesis screens can be used to find the the role and function of genes in the cell cycle G1 S G2 M wild-type G1 phase cdc mutant S phase cdc mutant G2 phase cdc mutant M phase cdc mutant Mutations in genes required for progression from a phase of the cell cycle to the next cause yeast cells to arrest at the specific point in the cell cycle 1 1) At permissive temp. Growth wild type yeast is comparable to growth mutant 2) However phenotype is visible during restrictive temp (to identify mutants) 3) Cells will arrest before a certain phase of the cell cycle 4) Therefore must have specific mutated gene (specific to missing that part cell cycle) 5) Non cdc genes identified cos arrest immediately upon transfer to restr. cond! Mutagenesis is just another word for occurance of a mutation Describe and explain how plasmid rescue can be used to identify key human genes (5) Will use cdc2 human gene as an example 1) Yeast cdc2 mutant gene grown in permissive conditions 2) Then transformed with plasmid library of human genes 3) Transformed cells shifted to restrictive temp (so can see phenotype) - only cells with transformed copy human cdc2 genes grew 4) This proves that human cdc2 gene can replace the mutated yeast cdc2 gene 5) Due to high conservation of human and yeast cdc2 genes
Explain how mutagenesis reveals the genes and proteins that regulate flower development carpel stamen petal sepal Flower Floral Diagram a b normal class a se - st - pe - ca ca - st - st - ca class b se - se - ca - ca - Genetic analysis has shown that there are 3 main mutations a flower can have (each having different whorl - pattern) carpel stamen petal sepal - All 3 will have a different order of structure so compare genotype to phenotype to identify genes and proteins involved C class c se - pe - pe - se Describe the ABC model and explain how mutant phenotypes reveal the genes and proteins that regulate flower development a ab = a bc = b C = C 8 ab bc C a - 6 normal b C bo bc a ab - c a ab bc C - - a class b
1) ABC model predicts where ABC (colour) genes are expressed -> showing how floral organ patterns can be arranged on a flower A -1st + 2nd B - 2nd + 3rd C - 3rd+4th whorl 2) It's a simple explanation based of mutagenesis screen 3) Model predicts that the A,B,C functions are expressed in 2 floral whorls and act together 4) Examination of ABC expression pattern confirms this