Question

For each of the following, briefly explain the major significance or importance to development

a) fetal hemoglobins

b) AGM (aorta/gonad/mesonephros)

c) fetal lung surfactant

d) ultrabithorax

e) inject bicoid into posterior of Drosophila zygote

f) foramen ovale and ductus arteriosus

Answer 1

a. Fetal hemoglobin has a high affinity for the oxygen than adult hemoglobin and hence it can hold the oxygen from the maternal circulation. This creat lower oxygen tension in the fetus. Low oxygen tension is important for the expression of factor hypoxia-inducible factor 1 (HIF1). This HIF1 is important for the growth of blood vessels during development.
b. AGM region provides the first autonomous intra-embryonic site for definitive hematopoiesis and hence it plays an important role in the development. Hematopoietic stem cells are produced from definitive hematopoiesis. These hematopoietic stem cells have the capacity to differentiate any cell lineage.
c. Fetus started generating surfactants while in the womb. Surfactant is composed of lipoprotein complex. In the lungs, it decreases the surface tension of the fluid. This increases the stability of the small air sacs in lung alveoli and prevents small air sacs from collapsing during exhales.
d. Ultrabithorax is the product of Ultrabithorax (Ubx) gene. Its importance is well studied in Drosophila. It begins abdominal development and repressing appendage development and hence has a role in the determination of segment identity in the abdominal and thoracic regions.
e. Bicoid regulates the production of anterior structures. And Caudal and Nanos have a function in the formation of the posterior parts of the embryo. Therefore injection of bicoid in the posterior part will not affect any developmental process.
f. These two structures develop in the prenatal heart that allows the flow of blood through the lungs. Foramen ovale is the shunt that bypasses the lungs. This shunt helps in the flow of blood from the right atrium of the heart to the left atrium. The ductus arteriosus helps in the flow of blood from the pulmonary artery to the aorta.