Enter your emailid Username. Login Here Create a new account. Mosaic and regulative eggs, Biology Assignment Help:. Mosaic and Regulative Eggs Eggs as well as early cleavage embryos are occasionally divided into two categories: i Mosaic or determinate embryos and ii Regulative or indeterminate embryos. Related Discussions:- Mosaic and regulative eggs Can you describe about hematosis, Q. In humans where doe Heliozoans - protozoan, Heliozoans - Protozoan Heliozoans are spherica Illustrate the functioning of living systems, How are buffers significant t Objectives of diabetes counselling, Objectives of Diabetes Counselling Chromosomes, Chromosomes Karl Nageli and Hofmeister observed chr Which kind of animals does the placenta exist, Q.
In which kind of animals Define mobilization of bone calcium and phosphorous, Define Mobilization of Explain the food applications of guar, Explain the Food Applications of gua Alteration of turgor of guard cells, Alteration of Turgor of Guard Cells Explain intensity of heart sound, Explain Intensity of heart sound? Write Your Message! Email id. Verfication Code. Featured Services. Online Tutoring. Project Development. The fate of the cell is governed entirely by its intrinsic characteristics, i.
During development each cell is said to undergo autonomous specification. If the cell is removed from the embryo it should, in principle, develop according to its intrinsic instructions and differentiate into the appropriate part of the embryo even if the rest of the embryo is not there. Most organisms contain tissues which may undergo one or both of these developmental mechanisms at a given time Gilbert, The developmental pattern of the amphibian heart will be studied by bisecting the heart primordial field and observing the subsequent development of the heart, if present.
If the heart were to develop using an autonomous mechanism, the cells would develop normally even if the two sides were not in physical contact with one another. This would lead to half a heart growing on either side of the incision. However, if instead the heart developed using a regulative mechanism, then the cells on the two sides would compensate for the perceived absence of the other cells. Even if there are no physical differences between the DNA of an egg and the DNA of a specialized somatic cell, how do we know all the DNA in the somatic cell is functional?
With plants, one cell any one can start over and regenerate a whole plant. Therefore all DNA in all cells of plant must be functional. Important point: the material in the cytoplasm of an egg is required to reprogram the nucleus -- to alter state of chromatin -- so nucleus can start over. This is what people usually mean when they talk about cloning a person or animal -- an adult nucleus is put into a anucleated egg, and the added genetic material drives development of a new complete organism.
This procedure -- nuclear transfer -- works, but with current technology it is very inefficient. Most transferred nuclei do not successfully produce an adult, probably because most nuclei are not reprogrammed successfully. The new adult is a "clone" of the adult that contributed the nucleus. However, the clone and the original will not be identical, just as "identical" twins are not exactly the same.
Also the clone and its parent may not have identical mitochondrial DNA. Should it be legal to clone your pet? Your child? What can we Conclude about Changes in Genes during Differentiation? Which genes are transcribed must change, not the genes. Exception: lymphocytes -- in these cells only, genes change as well as gene expression. In other words, how lymphocytes specialize is NOT the norm. The pattern of transcription must be stable under normal conditions so for example liver cells do not change into kidney cells.
The pattern of transcription is not fixed irreversibly see results above , although we don't fully understand the conditions needed to establish or change it. These modifications do correlate with changes in gene expression in many cases.
However, it is not clear if these modifications trigger changes in gene activity or changes in gene activity due to other signals result in these modifications. What is cause, and what is effect here? Note: Some organisms survive and develop perfectly well without methylating their DNA. How are the differential patterns of transcription set up? In problems, ignore any questions on instructive vs. Close cell contact required because signals are either paracrines or juxtacrines on surface of signaling cell.
Signals and receptors are evolutionarily conserved -- Have signal from mouse mesoderm that normally induces production of hair in mouse ectoderm. Position of determinants sets fate of cells in that part of the egg. Case like this: determination of location of germ cells by germ plasm.
Often have gradients of mRNA to be translated after fertilization or protein in the egg. See bicoid in text. After cleavage, different cells have different concentrations of cytoplasmic determinants, morphogens, etc. Start a sequence of sequential gene activations. Different TF genes turned on in dif.
Each active TF or combo turns on a different sets of genes all those with enhancer for that TF.
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