171.

Human sperms are allowed to fertilize ova having non functional ovastacin. The following possibilities may be of significance in the fusion of these gametes:

(a) The sperms will not fertilize ova.

(b) The sperms will blind and penetrate the zona pellucida but will not be able to fuse with ovum membrane.

(c) ZP2 will not be clipped by cortical granuel protease.

(d) CD9 protein of egg membrane microvilli will not be able to interact with sperm membrane proteins in the absence of ovastacin.

(e) Polyspermy may occur frequently.

Which combination of statements represent the outcome of the event?

(a) and (b)
(a) and (e)
(c) and (d)
(b) and (e)

172.

The zygote of C.elegans exhibits rotational cleavage. When the first two blastomeres formed (P1 and AB) are experimentally seperated, the following outcomes may be possible:

(a) The P1 cell in isolation generates all the cells it would normally make, showing autonomous specification

(b) The P1 cell in isolation generates all the cells it would normally make, showing conditional specfication

(c) The AB cell is isolation generates a small fraction of cell types it would normally make, showing conditional specification

(d) The AB cell in isolation generates a small fraction of cell types it would normally make, showing autonomous specification

Which one of the above combination of statements is true?

(a) and (c)
(b) and (c)
(b) and (d)
(a) and (d)

173.
Given below are some of the statements regarding regeneration:
(a) The type of regeneration characteristic of mammalian liver is considerd as Compensatory regeneration
(b) Regrowth of hair shaft from follicular cells exemplifies stem cell mediated regeneration
(c) Regeneration occuring through the repattering of existing tissues with little new growth is known as morphallaxis
(d) Adult structures undergoing dedifferentiation forming a blastema, that then redifferentiates to form the lost structure, is called epimorphosis
Choose the most appropriate combination of correct statements:

(d) only

(c) and (d) only

(a) , (b) and (c) only

(a) , (b) , (c) and (d)

D.

(a) , (b) , (c) and (d)

Regeneration is the ability of the fully developed organism to replace tissues, organs, and appendages. Some amphibians like salamanders show a remarkable capacity for regeneration, being able to regenerate complete new tails and limbs as well as some internal tissues. Some insects and other arthropods can regenerate lost appendages, such as legs. Another striking case of regeneratio in vertebrates is the zebrafish, which can regenerate the heart after removal of part of the ventricle.

Compensatory regeneration is regeneration in which cells divide, but maintain their differentiated function; they produce similar to themselves and do not form a mass of undifferentiated tissue; characteristics of mammalian liver generation.

Regrowth of hair shaft from follicular cells exemplifies stem cell mediated regeneration. The stem cells that regenerate a frog tail and a salamander limb have very different properties from a planarian stem cell . These multipotent tissue-specific stem cells are probably very similar to the stem cells in our own bodies that renew or repair tissues such as our skin or muscle.

Regeneration could lead to progress in the development of medical ways of repairing tissues such as the mammalian heart and the spinal cord. A distinction has been drawn between two types of regeneration. In epimorphosis, regeneration involves growth of a new, correctly patterned structure as limb. In morphallaxis, there is little new cell division and growth, and regeneration of structure occurs mainly by the repatterning of existing tissue; regeneration of the head in Hydra is a good example.

The cellular events during regeneration may be considered under two headings, regeneration events in the blastema starting from a wound surface, commonly called epimorphosis, and regeneration events in the old tissues, commonly called morphallaxis.

The mechanism involves ther dedifferentiation of adult structures to form an undifferentiated mass of cells that then becomes respecified. This type of regeneration is called epimorphosis and is characteristic of regenerating limbs. When and adult salamander limb is amputated the remaining cells are able to reconstruct a complete limb, with all its differentiated cells arranged in the proper order. In other words, the new cells construct only the missing structures and no more. For example, when a wrist is amputated, the salamander forms a new wrist and not a new elbow.

174.

Following are certain statements regarding apomixis in plants:

(a) Apomixis cannot be used to mantain hybrid vigor over many generations in plants

(b) In sporophytic apomixis maternal genotype is maintained

(c) There is an event of meiosis during gametophytic apomixis and is also referred as apomeiosis

(d) In diplospory, meiosis of the megaspore mother cell is aborted, resulting in two unreduced spores, out of which one forms the female gametophyte

Which one of the following combinations is correct?

(a) and (b)
(a) and (c)
(b) and (c)
(b) and (d)

175.

The following assumptions were derived from the above experiment:

(a) Medium A contained bFGF and PDGF.

(b) Medium b contained retinoic acid.

(c) Cells cultured in medium B were determined to become functional neurons prior to addition of the medium.

Which one of the following combinations represents correct statements?

(a) and (b) only
(a), (b) and (c)
(b) and (c) only
(a) and (c) only

176.

Following statements were made with respect to symbiotic association of rhizobia with legumes:

(a) nodD is regulatory gene.

(b) Nod factors are lipochitin oligosaccharides.

(c) Nod factors predominantly have α-1→ 4 linked N-acetyl-D-glucosamine backbone.

(d) Receptors for Nod factors are protein kinases with extracellular sugar-binding Lys M domain.

Which one of the following combinations represents all correct statements?

(a),(b) and (c)
(a),(c) and (d)
(b),(c) and (d)
(a),(b) and (d)

177.

In case of hydra, the major head inducer of the hypostome organizer is a set of Wnt proteins acting through the canoniocal β-catenin pathway. What would be the result, if a transgenic Hydra is made to globally misexpress the downstream Wnt effector β-catenin?

Ectopic buds will be formed all along the body axis and even on the top of the newly formed buds
Ectopic tentacles form at all levels
Both ectopic tentacles and buds would be formed along the body axis
There woulod be no change observed

178.

Both TGF-β are Sonic hedgehog signals play important roles in both neuralation and cellfate patterning of the neural tube. Which one of the following statements is true?