Hox genes that are responsible for the organization of posterior structures: a.

Question

Hox genes that are responsible for the organization of posterior structures:

a. are expressed earlier in development

b. are expressed only whe high levels of retinoic acid are present

c. are expressed later in development

d. are expressed only when low levels of retinoic acid are present

e. both b and c

In the development of the pituitary gland, the ventral outpocketing from the floor of the diencephalon will give rise to the

a. infundibulum

b. anterior pituitary

c. rathke's pocket

d. hypothalamus

e. none of the above

The sinus venosus of the embryonic heart

a. atrophies and disapears in the adult mammalian heart

b. initiates the regular beating pattern of the adult mammalian heart

c. becomes part of the wall of the right atriumin the adult mammalian heart

d. becomes the sino-atrial node of the adult mammalian heart

e. all but a

The ductus arteriosus connects the

a. pulmonary artery with pulmonary vein

b. aorta with pulmonary artery

c. aorta with pulmonary vein

d. umbilical vein with aorta

e. none of the above

Hox genes are responsible for

a. limb bud organization

b. cardiac mesoderm organization

c. lens induction

d. antero-posterior organization

Explanation / Answer

1. Hox genes that are responsible for the organization of posterior structures:

a. are expressed earlier in development

HOX genes homeotic genes are expressed during the early development of embryo and is continuous in the later life of animals. HOX genes are specifically responsible for antero-posterior axis organization. Any change in expression of HOX genes causes changes in specific segmental segmental patterns of the organism..

The ductus arteriosus connects the

b. aorta (Proximal descending aorta) with pulmonary artery

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