The cell death pathway in C. elegans can be schematically represented as:

Based on the above, which one of the following is TRUE?

• A loss-of-function allele of ced9 would lead to survival of cells that normally die

• A loss-of-function allele of ced9 would lead to excessive cell death.

• A gain-of-function allele of ced9 would lead to excessive cell death.

• Neither loss or gain-of-function of ced9 would make any change to the cell death pathway.

Hensen's node is established as the avian equivalent of the amphibian dorsal blastophore lip. The following observations are presumed to be in support of the same.

A. It is the region whose cells can both induce and pattern a second embryonic axis when transplanted into other locations of the gastrula.

B. It is equivalent in terms of tissue structure.

C. It expresses the same marker genes as the Spemann's organizer in amphibians.

D. The same micro RNA can interfere with the formation of pre-chordal plate in both Hensen's node and Spemann's organizer.

Choose the correct set among the following:

• A and D

• A and C

• B and C

• A and B

In amphibians, when due to some injury, the eye lens is damaged, the fully differentiated iris cells can regenerate the lens. It is achieved through the following possible processes:

A. Iris cells through some signaling undergo differentiation and transdifferentiation into lens cells to regenerate the lens.

B. Iris cells transform into lens spontaneously.

C. Iris cells induce in a stepwise manner, specific genes responsible for their differentiation and then conversion to lens cells.

D. Stem cells present in iris tissue differentiate into lens cells.

Which of the following is correct?

• A and B

• A and C

• B and D 

• B and C

The control of flowering is a complex process involving several key regulatory genes. Some statements on flower development are given below:

A. Two major types of genes regulate floral development: meristem identity genes and floral organ identity genes.

B. The important genes in Arabidopsis that play key regulatory roles in meristem identity are:

APETALA1, LEAFY and SUPPRESSOR OF CONSTANS1.

C. The genes that determine floral organ identity were discovered as floral homeotic mutants.

D. Most plant homeotic genes belong to a class of related sequences known as FAD box genes.

Which one of the following combinations of the above statements is correct?

• A, B and C

• B, C and D

• A, C and D

• A, B and D

65.

A few statements on early developmental stages in plants are given below:

A. The cells of flower are diploid in nature.

B. Only some specialized cells in the reproductive organs undergo meiosis to produce haploid cells.

C. The haploid cells produced in (B) above, undergo a few normal mitotic cell divisions.

D. All the progeny cells produced in (C) above, differentiate either into haploid egg cells or haploid sperm cells.

Which one of the following combinations of the above statements is correct?

• A, B and C

• B, C and D

• A, C and D

• A, B and D

Cells from an early frog blastula were removed from the animal pole and used to replace cells from the vegetal pole of the blastula. The following events may be expected.

A. Transplanted cells would develop normally as part of the cells of the vegetal pole.

B. Transplanted cells would develop as cells of the animal pole of the adult on the vegetal pole.

C. Region of the animal pole from where the cells were removed would be missing in the adult.

D. Remaining cells in the animal pole would compensate for the cells that were removed.

Which of the following are true?

• B, C and D

• A, B and D

• A, B and C

• A, C, and D

Capacitation of mammalian sperms allows them to be activated within the uterus and facilitate fertilization. The following statements were made regarding events occurring during capacittaion:

A. Removal of cholesterol from sperm head.

B. Removal of non-covalently bound glycoproteins.

C. Increased expression fibronectin.

D. Decreased permeability of calcium ions.

Identify the correct statements.

• B, C, and D

• A, B, and D

• A, B, and C

• A, C, and D

Which one of the following is developmental processes in animals is more dependent on cellular movements?

• pattern formation

• morphogenesis

• cell differentiation

• growth

Engrailed expression in Drosophila melanogaster defines

• anterior margin of the segment

• anterior compartment of each segment

• posterior margin of each parasegment

• posterior compartment of each segment

During which one of the following stages of Arabidopsis embryogenesis, cell elongation throughout the embryonic axis and further development of the cotyledons occur?

• globular stage

• torpedo stage

• heart stage

• mature stage