L15 Flashcards
somites are discrete blocks that develop in a ________ to _______ direction
anterior
posterior
what are some of the fates of somites?
vertebrae and ribs
dermis of the dorsal skin
skeletal muscles of the back
skeletal muscles of the body wall and limbs
can the somites that form cervical vertebrae of the neck and lumbar vertebrae of the abdomen form ribs?
no - they are only generated by somites forming the thoracic vertebrae
somites already contain positional info prior to their formation t or f
t
more _______ strcutres express a greater number of Hox genes
caudal
hox code: is it discrete, combinatorial, or posterior prevalance?
all three probably - but posterior prevalence increasingly important in caudal structures
normal anterior boundary of Hoxa7 expression is in the ____ region
thoracic
ectopic expression of Hoxa7 throughout the whole AP axis will transofmr the ______ of the skull, into a _____ structure, which is next more posterior structure
basal occipital bone
pro-atlas
3’ genes affect the ____ structures, and the 5’ genes affect more _______ structures
anterior
posterior
paralogous genes from different clusters have some overlapping functions - what is this called?
redundancy
most __________ expressed gene imposes its function over that of more ________genes
posterior
anterior
_____ exposure results in homeotic transformations
RA
high [ ] of ______ administered in utero causes misexpression of ______, which results in developmental transformations similar to over (ectopic) expression of these genes
hox genes
in normal development length of exposure to high retenoic acid may specify fate along the _____ axis
AP
RA activates HOX genes _______
sequentially
in chick embryo, somites express _______, which generates RA from vitamin A. this induces gene expression of genes with _____ elements
retinaldehyde dehydrogenase
RARE
vertebrate clusters for hox genes are more __________ than drosophila, and there is _____ regulatory elements in vertebrae whereas there is _______ regulation in drosophila.
compact
shared
independent
hox domains are established by ____ and ________ genes in drosophila, but this process isn’t completely understood in vertebrates. appears to depend on ____ and ___________
gap
pair-rule
somitogenic clock
retinoic acid levels
vertebrate hox complex comprises _____ clusters
4 (A-D)
