List at least three stages in gene expression that can be regulated to result in differentiated cell types? Explain any one of them with the help of an example.

Mention the two types of endoskeletal structures found in vertebrates. What is the difference between their ground matrix?

Mark the following statements as ‘True’ or ‘False’:
i) During development cells move by extending their cell processes in all directions without any polarity.
ii) The cytoskeleton of the cell is actively involved in cell movement and cell shape change.
iii) Cadherin on one cell binds strongly to similar cadherins molecules on other cells.
iv) Integrins are cell adhesion molecules that attach cells to other cells at the apical region.
v) Permissive interaction involves gene expression in the induced cell.
vi) Morphogens are paracrine signalling molecules.
vii) In apoptosis the cell organelles are delivered to lysosomes and the cell contents are spilled out.
viii) Cell death by necrosis indicates that cell has undergone a toxic reaction.
ix) Optic cup is induced to form the retinal layers by reciprocal induction from the lens.
x) Pattern formation is the result of morphogenesis.

Describe the process of neurulation in chick.

Fill in the blanks in the following sentences by selecting an appropriate word from those given in the parenthesis after each sentence:

i) The skeleton of the head is known as ……………………. (vertebral column, pelvic girdle, skull).

ii) Cranium encloses and protects the ……………………… (eye, heart, brain).

iii) The brain within the cranium is in contact with the spinal cord through ………………………… an aperture found at the hind end of the cranium (fenestra ovalis, foramen magnum, external nares).

iv) The vertebra with concavity infront and convexity behind is called …………………. type (amphicoelous, procoelous, opisthocoelous).

v) The bone humerus of the upper arm articulates with the pectoral girdle at ……………………… cavity (glenoid, acetabulum, zygapophysis).

vi) Radio-ulna, a composite bone is found in ……..…………….. (rabbit, bat, frog).

What are the major differences in the development and differentiation of an egg and a sperm?

How is the placenta formed? What are its functions?