Question

Fate map of embryo is prepared in which stage?
A. Morula
B. Blastula
C. Gastrula
D. Neurula

Answer 1

Hint:- Fate mapping is the technique used to determine the fate of every tissue in an embryo in its developmental stage. Different organs and organ systems develop from a group of tissues. Which part of the embryo develops into which tissues are studied. This development study is done by comparing the state of tissues in different stages of development in an embryo.

Complete solution:
The single-celled zygote formed after fertilization undergoes holoblastic equal cleavage and becomes blastomeres. The 2,4,8 and 16 cells are called blastomeres. By further cleavage, a solid mass of 8 to 16 blastomeres called morula develops. The morula develops into a blastula. Inside the blastula, there is a blastocoel of the blastocyst. The blastocyst is a mass of cells that is differentiated into an outer trophoblast and an inner embryoblast. Cell differentiation is initiated in the blastula stage and therefore fate mapping is prepared by observing the embryo from the blastula stage. Trophoblast cells develop further and play an important role in the formation of the placenta.
In gastrulation, cells of the blastula move inward like an invagination forming different layers called the germ layers. In humans, the development of three germ layers is seen, called triploblastic. The embryo during gastrulation is called the gastrula. The 3 germ layers are ectoderm, mesoderm, and endoderm. Gastrulation is followed by neurulation in which the neural tube of the embryo is developed. Embryo at this stage is called neurula. This stage is the beginning of organ formation. Later the remaining organs and organ systems are developed.
So, the correct answer is option B.

Note:- When fate mapping is done on a single cell scale, it is called cell lineage. In cell lineage relations between several cells are studied and in fate mapping fate of the blastocyst into tissues are studied. Fate mapping is relevant now in the study of tumors, cancer biology, stem cell research, etc. Tissues in different stages are studied by tagging the cells using dyed agar chips or molecular barcodes.