The H3.H4 tetramers and H2A.H2B dimers each interact with a particular region of the DNA within the nucleosome.

I. Histone H3.H4 tetramers occupy a key position in the nucleosome by binding the middle and both ends of the DNA.

II. The amino-terminal region of H3 most proximal to the histone-fold region forms a fourth a-helix that interacts with the final 13 bp at each end of the bound DNA.

III. The relatively short length of DNA bound by H2A.H2B dimers is sufficient to prepare the DNA for H3.H4 tetramer binding.

IV. The H3.H4 tetramer forms the bottom part of the histone octamer located across the disc from the DNA ends whereas two H2A.H2B dimer occupies the top part.

Which of the following represents the correct binding of the histones with the DNA?

TLS Online TPP Program

#Question id: 5238

#Unit 5. Developmental Biology

all tissue types possess a unique stem cell niche, and despite many differences among the niche architecture of different tissues, several common principles of stem cell regulation can be applied to all environments. These principles involve extracellular mechanisms leading to intracellular changes that regulate stem cell behavior.

Column A	Column B
I. Extracellular regulatory mechanisms	i. Regulation by endocrine, paracrine, or juxtacrine mechanisms
II. Intracellular regulatory mechanisms	ii. Regulation by a network of transcription factors
	iii. Epigenetic regulation
	iv. Regulation by cell-to-cell and cell-to-matrix adhesions
	v. Regulation by cytoplasmic determinants

Match the following regulatory mechanism (column A) with the factors that regulate stem cell behavior (column B).

TLS Online TPP Program

#Question id: 5254

#Unit 5. Developmental Biology

Following signal transduction pathways can be grouped into several basic types, based on the sequence of intracellular events.

According to above figure, which of the following correctly represents the basic concepts of all signalling pathway?

TLS Online TPP Program

#Question id: 14706

#Unit 5. Developmental Biology

Match the types of cell movement during gastrulation

TLS Online TPP Program

#Question id: 14707

#Unit 5. Developmental Biology

Which of the following organ belongs to the internal layer of gastrula?

TLS Online TPP Program

#Question id: 14708

#Unit 5. Developmental Biology

Difference between gastrulation in Xenopus and sea urchin;

I. In Xenopus, formation of blastopore: mesoderm and endoderm move inside by involution over blastopore lip.

II. In sea urchin, formation of blastopore: mesodermal cells migrate into the interior; endoderm moves inside by invagination of the epithelial sheet.

TLS Online TPP Program

#Question id: 14709

#Unit 5. Developmental Biology

Choose right statement about cleavage pattern and gastrulation movements;

1.At the end of cleavage the animal embryo is essentially a closed sheet of cells, which is often in the form of a sphere enclosing a fluid-filled interior. Gastrulation, strictly the formation of the gut, converts this sheet into a solid three-dimensional embryonic animal body. 

2.During cleavage, cells move into the interior of the embryo, and the regions of endoderm. and mesoderm. which were originally adjacent in the cell sheet, take up their appropriate positions in the embryo.

3. Gastrulation results from a well- defined spatio-temporal pattern of change in cell shape, cell movement, and change in cell adhesiveness, the main forces of which are generated by localized contractions.