​A type of regeneration in which the differentiated cells divide, maintaining their differentiated function without dedifferentiation and production of undifferentiated mass, is known as​

​Given below are statements related to expression of some of the pattern-forming genes in vertebrate limb bud:​

​A. Lmx1b gene is expressed in dorsal mesenchyme
B. Shh is expressed in the posterior region
C. Wnt7a gene is expressed in dorsal ectoderm
D. Hoxa13 and Hoxd13 are expressed in the distal region
E. Tbx5 and FGF10 are expressed in the lateral plate mesoderm involved in formation of limb bud​

​The Nail-Patella syndrome in humans and the syndrome in mice exhibiting footpads on both dorsal and ventral surfaces of the limb are associated with which of the above-mentioned gene functions?​

​The early embryonic development in amphibians and aves serves as two different model plans of development. In the former, the germ layer formation is initiated from a fluid-filled ball-like blastula, while in the latter the germ layer formation is initiated on a flat blastodisc. Given below are some of the terms for amphibian embryo in column I and from avian embryo in column II:​

​Which of the following is the all-correct match of Column I with Column II?​

The specification of sea urchin micromeres involves the activation of a repressor protein Pmar1, which represses the expression of hesC, which also encodes a repressor protein. One of the genes controlled by HesC is Delta, whose expression is used as a marker for micromere lineage. The image below represents a sea urchin embryo on which whole mount in situ hybridization (WMISH) was performed using delta probe, indicated by the area ‘A’. The rest of the embryo is labeled ‘B’.​

​(Image from Revilla-i-Domingo et al (2007), PNAS 104:12383-12386)​

​The table below summarizes a set of experiments (column A) and the area in which hybridization is observed (column B)​

​Which one of the following options is a correct match between columns A and B?​

In an experiment, activin-secreting beads were placed on unspecified cells from an early Xenopus embryo. The activin then diffused from the beads. If the beads contained 1nM of activin, it elicited expression of Xbra gene in cells near to the beads. If the beads contained 4nM activin, the expression of Xbra was elicited in cells, but only at a distance of several cell diameters away from the beads. In the latter case, expression of goosecoid gene was observed near the source bead. Beads with no activin did not elicit the expression of the two genes.​

Which of the following statements are correct?

A. High concentration of activin activates goosecoid, whereas lower concentrations activate Xbra
B. Lower concentrations of activin help specify the dorsal-most structures of the frog’s embryo
C. Concentrations of activin that do not lead to expression of the two genes specify the cell to become blood vessels and heart​

​Select the correct answer:​​

​What would be the effect of retinoic acid (RA) treatment on the ‘positional information’ of blastema cells present on the amputated newt limb?​

Given below are some of the statements in connection with neural tube formation in vertebrates:

A. In primary neurulation the cells surrounding the neural plate direct the neural plate cells to proliferate, invaginate and separate from the surface ectoderm to form an underlying hollow tube.
B. In secondary neurulation the neural tube arises from the aggregation of mesenchyme cells into a solid cord that subsequently forms cavities to create a hollow tube.
C. In birds primary neurulation generates the neural tube from anterior up to the hind limb developing region.
D. In mammals, secondary neurulation begins at the level of sacral vertebrae.
E. Anencephaly results when a failure to close the neural tube occurs, resulting in the forebrain remaining in contact with amniotic fluid.

Which one of the following options gives all correct statements?

​Match the terms used in vertebrate limb development in List I with their descriptions in List II:​

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

​

The Dorsal protein is involved in generating the dorsal-ventral (DV) polarity in Drosophila. The following statements were made regarding the activity of the Dorsal protein in establishing the DV polarity.

A. In embryos that lack Gurken protein, the Dorsal protein is not translocated to the nucleus of the follicle cells which then causes ventralization of the embryo.
B. Though Dorsal protein acts as a morphogen, it is found throughout the syncytial blastoderm of the early Drosophila embryo.
C. In embryos that lack Cactus protein the Dorsal protein can be found in the nucleus of cells with a ventral fate.
D. If the Dorsal protein is blocked from entering the nucleus, the genes responsible for specifying dorsal cell types are not transcribed.

Which of the above statements are correct?

​Which one of the following statements is NOT correct regarding the tetrapod limb development?​

​In a transplantation experiment, the area of presumptive ectoderm from an early frog gastrula was transplanted to a region of the newt gastrula destined to become parts of the mouth. The resulting salamander larvae had frog-like mouth parts (frog tadpole suckers) instead of balancers as observed during development of wild type newt embryo. This is an example of:​