L15

Question 1

somites are discrete blocks that develop in a ________ to _______ direction

Answer 1

anterior
posterior

Question 2

what are some of the fates of somites?

Answer 2

vertebrae and ribs
dermis of the dorsal skin
skeletal muscles of the back
skeletal muscles of the body wall and limbs

Question 3

can the somites that form cervical vertebrae of the neck and lumbar vertebrae of the abdomen form ribs?

Answer 3

no - they are only generated by somites forming the thoracic vertebrae

Question 4

somites already contain positional info prior to their formation t or f

Answer 4

t

Question 5

more _______ strcutres express a greater number of Hox genes

Answer 5

caudal

Question 6

hox code: is it discrete, combinatorial, or posterior prevalance?

Answer 6

all three probably - but posterior prevalence increasingly important in caudal structures

Question 7

normal anterior boundary of Hoxa7 expression is in the ____ region

Answer 7

thoracic

Question 8

ectopic expression of Hoxa7 throughout the whole AP axis will transofmr the ______ of the skull, into a _____ structure, which is next more posterior structure

Answer 8

basal occipital bone
pro-atlas

Question 9

3’ genes affect the ____ structures, and the 5’ genes affect more _______ structures

Answer 9

anterior
posterior

Question 10

paralogous genes from different clusters have some overlapping functions - what is this called?

Answer 10

redundancy

Question 11

most __________ expressed gene imposes its function over that of more ________genes

Answer 11

posterior
anterior

Question 12

_____ exposure results in homeotic transformations

Answer 12

RA

Question 13

high [ ] of ______ administered in utero causes misexpression of ______, which results in developmental transformations similar to over (ectopic) expression of these genes

Answer 13

hox genes

Question 14

in normal development length of exposure to high retenoic acid may specify fate along the _____ axis

Answer 14

AP

Question 15

RA activates HOX genes _______

Answer 15

sequentially

Question 16

in chick embryo, somites express _______, which generates RA from vitamin A. this induces gene expression of genes with _____ elements

Answer 16

retinaldehyde dehydrogenase
RARE

Question 17

vertebrate clusters for hox genes are more __________ than drosophila, and there is _____ regulatory elements in vertebrae whereas there is _______ regulation in drosophila.

Answer 17

compact
shared
independent

Question 18

hox domains are established by ____ and ________ genes in drosophila, but this process isn’t completely understood in vertebrates. appears to depend on ____ and ___________

Answer 18

gap
pair-rule
somitogenic clock
retinoic acid levels

Question 19

vertebrate hox complex comprises _____ clusters

Answer 19

4 (A-D)