Question

•Predict the phenotype of a mouse ectoderm in an embryo harboring a mutation that alters BMP concentration

-Predict the phenotype of an organism exhibiting mutations in Shh, BMP4/7, E-cad, N-cad

-Compare the differences in cell behaviors and architecture between primary and secondary neurulation

Answer 1

part 1- absence or less concentration of BMP , increases the length of nerve cord significantly to move to ventral side that is why very less epidermal tissues are formed, and there will be a unviable embryo.

part 2- if the organism exhibiting mutation in shh(sonic hedge hog) there will be a development of single large eye at the center of the forehead( cyclopia).and shh is an inhibitor of pax6. shh is responsible for multiple fuctions , mutation it it halters all these functions . functions of shh are- develops anterio-posterior polarity in limb and also identify the position of pinkie finger, development of hair in mammals, development of feathers in birds and their positioning.

organism exhibiting mutation in BMP4 , there will be no lens induction and will not specify epidermis.

organism exhibiting mutation in BMP7- will not induce apoptosis, there will be no kidney formation and sperm formation.

organism exhibiting mutation in e-cad(CDH1) causes gastric cancers and lobular breast cancers.

organism exhibiting mutation in n-cad(CDH2) causes dilated cardiomyopathy.

part 3-

process by which neural tube is formed by the bneural plate is called neurulation. a portion of the dorsal ectoderm is specified to become neural ectoderm during the third week of gestation, this region of embryo is known as neural plate. this process is done by 2 ways.
primary neurulation: surrounding neural plate cell causes neural plate cells to proliferate, invaginate, and pinching off from the surface to from neural plate . this process divide into four spatio-temporal overlapping stage- formation of neural plate
shaping of neural plate
bending of neural plate to form neural groove
closure of the neural groove to neural tube.
secondary neurulation: it involves the formation of medullary cord and a rod like condensation of mesenchymal cells is formed under the dorsal ectoderm, within mesenchymal rod cavitation process forms a central canal , this canal gets continued with the one which formed during primary neurulation. this process is not that prominent.