morphogens induction and competance Flashcards
what is morphogen?
chemical (usually diffusable signalling molecule produced from a localised source whose concentration varies through embyro and froms a conc gradient
substance active in pattern formation whose spatial concentration varies to which cells respond differently to different threshold concentrations
give 3 characteristics of a morphogen
produced from a localised source , produces a conc gradient throughout model and specifies cell fates according to concentration
what is model to represent cells responces to morphogen?
french flag model
what does french flad model account for?
regulative development - if line cut in half ystem will regenerate. if length of line varies-pattern will regenerate
give 3 mechanisms in which transport of morphogen can occur/
diffusion
endocytosis
extra cellular matrix
what is bicoid?
maternal protein/transcription factor that acts as a morphogen and forms a gradient via cytoplasmic diffusion in syncytial blastoderm.
what does bicoid activate?
activate expression of hunchback gene in nucleus
what does hunchback code for?
another transcription factor - cascade of genes that establish segmentation
what is induction?
signalling of one cell type to another with a change in specification of a responding cell/tissue
what is competance?
the ability to repsond to a signal
what does xenopus animal cap assay show?
animal cells are fated to become neural and epidermis but can be induced to become muscle with vegetal cell signals. (animal cells competants)
why do animal cap cells not usually become muscle?
as blastocoel separates animal and vegetal poles
what do vegetal cells give rise to when combined with animal cells?
dorsal - notchocord and muscle
ventral - blood
