DEVELOPMENT The egg cell provides the molecular and architectural context for development IMPORTANT ISSUES 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 The Drosophila egg has maternal gene products localized 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 ALL LETHAL and 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 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 WILD TYPE YELLOW Sn Sn y y Sn sn y Y Sn y Sn y Sn y sn Y sn Y sn Y sn Y Sn y sn Y SINGED sn Y sn Y Sn WILD TYPE y Sn y Sn y Sn y sn Y sn Y sn Y sn Y Sn y 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 A CELL TYPE SPECIFIC PROMOTER DRIVES CRE EXPRESSION
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