DEVELOPMENT The egg cell provides the molecular and architectural context for development IMPORTANT ISSUES The Drosophila egg has maternal gene products localized 1 The egg has information pre stored in it How do we identify the genes encoding this information 2 Not all genes are expressed in each cell tissue How do we determine whether a gene is required for a particular developmental event 1 The Drosophila egg has maternal gene products localized MATERNAL EFFECT MUTATIONS IDENTIFY DEVELOPMENTAL GENES WHOSE PRODUCTS ARE PRE LOCATED IN THE EGG ZYGOTIC LETHAL lethal MATERNAL EFFECT LETHAL X lethal 3 viable 1 dead MATERNAL EFFECT LETHAL Can the mother produce normal eggs lethal X lethal lethal lethal lethal ALL VIABLE lethal X lethal lethal lethal X ALL VIABLE lethal lethal X ALL LETHAL and ALL LETHAL 2 HOW CAN WE DETERMINE WHETHER A GENE S FUNCTION IS AUTONOMOUS OR NON AUTONOMOUS A CELL OR TISSUE MAY RECEIVE INFORMATION 1 FROM THE CELL ITSELF AUTONOMOUS 2 FROM ITS NEIGHBORS NON AUTONOMOUS 3 MITOTIC RECOMBINATION Sn y sn Y Sn y Sn Sn y sn Y sn Y Sn y sn Y sn Y X HOW CAN WE TELL IF A GENE FUNCTION IS REQUIRED IN A SPECIFIC TISSUE y ANSWER GENERATE MUTANT CLONES WITHIN THE TISSUE Sn sn sn Sn y y Y SINGED y Sn Y sn sn y Sn y Sn y sn Y sn Y sn Y sn Y Sn y WILD TYPE YELLOW Sn Sn y Y Y Sn sn y Y Sn y sn Y sn Y Sn y sn Y Sn y WILD TYPE 4 HOW CAN WE TELL IF A GENE PRODUCT IS REQUIRED IN A PARTICULAR TISSUE METHOD USE THE CRE LOX SYSTEM TO ELIMINATE THE GENE ONLY IN THAT TISSUE CRE IS A RECOMBINASE CAUSING RECOMBINATION ONLY BETWEEN TANDEMLY REPEATED LOX SITES HOW CAN WE DELETE A GENE IN A PARTICULAR TISSUE METHOD PLACE CRE UNDER A TISSUE SPECIFIC PROMOTER AND THE GENE IN QUESTION FLANKED BY TANDEM LOX SITES 5 A CELL TYPE SPECIFIC PROMOTER DRIVES CRE EXPRESSION 6
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