Developmental Genetics and age of mutants IIA

genes

thought came from cytoplasm

these cytoplasmic factors could control cell fate

tought variations were too subtle

political

two demands

needed to show could control earliest most basic phases of development

how chromosomes indential in every cell type can produce cytoplasm with different properties

mouse mutation Brachyury

heterozygoud mice - short tail

homozygous - die before birth

brachyury mutants aka T have defects in posterior part early embryo

disruption of notochord

fly mutations affect wing development

experiments to prove

regeneration experiments

loss of limbs of salamanders

cloning of somatic nuclei

albino parents of nucleus donor to wild type donor of enucleated eggs

are all albino

genes act in both early and late stages of development

showed genes are regulated differently in different cell types during devlopment

still question of nature vs nurture

characterized homeotic genes that act later in development

maternal acting genes that control earliest stage sof development

A) loss of function reveals normal functionc

reverse genetics and knockouts

requires no previous information

enough genetic info, specific gene disrupted can be indetified and studied molecularly

pleiotropy

many mutant embryos die

genes are invovled many tissues, hard to implicate one

redundancy

genes in parallel don't show phenotype until entire set knocked out

only works in few animals or plants

need sort generation time and easy lab culture

based on mom, must be homozygote dominant mutant for offspring to express trait