Introduction:
All the organisms on this earth begin from a single cell. These single cells carry the DNA (Deoxyribonucleic acid) coding for all the proteins the adult organisms will use. However, if these single cells expressed all of these proteins at once, they would not be functional. So this cell must divide repeatedly and the cells must begin the process of cell differentiation as and when they divide. The cell lines then begin to emerge, and the cells become more and more specific. Eventually, an entire organism is formed with hundreds of different types of cells from this process of cell differentiation.
Body:
The original mass of cells, which do not undergo any differentiation, are known as stem cells. Unlike the normal cell division process, which creates two identical cells known as daughter cells, the division of stem cells is asymmetric cell division. In this type of case, one of the daughter cells remains identical to the parent stem cell. In the other cell, chemical triggers activate the process of cell differentiation and the cell starts to express the DNA of a specific cell type. Stem cells that can differentiate into entire organisms are known as embryonic stem cells and are said to be totipotent (a single cell that can give rise to a new organism).
By contrast, the body also has many cells that are only pluripotent (cells that can self-renew by dividing) . These cells have already undergone some type of cell differentiation. They can only divide into a narrow range of cell types. Bone marrow contains in it somatic stem cells, which can only become red blood cells. These cells are very necessary for the constant replenishment of blood cells, which are mostly inactive besides their oxygen-carrying ability.
Cell Differentiation in animals
After the completion of the process of fertilization in animals, a single-celled organism called the zygote is formed. This zygote is totipotent and it eventually becomes an entire organism. Even the largest animal found on Earth, the blue whale, also starts as a single cell. The complex tissues and organ systems, which are completely different in their formation and function, all come from the zygote. The process of cell differentiation starts at an early age within the organism. When the gastrula is formed, the cells have already started expressing various portions of the DNA.
These changes drive the processes within the embryo. As the tissues continue their formation, some cells start releasing hormones or chemical triggers that signal various cells to react. Hormone signals guide DNA expression in various parts of the body, which moderate their cell differentiation further. In humans it requires a little over a month for an immature heart and circulatory system to form.
Cell Differentiation in plants
The process of cell differentiation is similar to the plant life cycle that seems to be complex.While there are different hormones involved, all plants also develop from a single cell. A seed acts as a protective house for the zygote, providing food supply to it. It is just similar to an egg in the animal field. The zygote inside the seed undergoes the process of cell division and eventually becomes a small embryo. Development is stopped for some time, as the seed is distributed around the world.
After winter or anytime the environment is prime, the seed soaks up moisture and restarts its process of development. The embryo begins to form two meristems. A meristem is a unique and important portion of stem cells, which undergo cell differentiation as they grow outward. One grows towards the surface, while the other becomes the roots.
A different layer of cells forms around the meristem in the roots, known as the root cap. This layer of cells gets removed by itself as the roots move through the soil, and are fairly replaced by the meristem. On the inner part of the meristem, cell differentiation happens in a different direction. The hormones and environment direct the cells to become vascular tissues and supporting cells. These eventually carry water and nutrients to the top of the plant.
On the surface, the meristem acts in a very similar way. As it breaks upward, it generates both inward and outward cells. The inward cells go through a differentiation similar to that of the differentiation of roots, creating more and more vascular tissues. The cells undergo cell differentiation into stems and leaves on the outer part. These are the same as the different organs of animals and are also as different from the starting cells as animal cells.
Cell Differentiation process
One of the main factors to the cell differentiation process is transcription factors. These hormones and chemicals direct the activities surrounding DNA, determining what gets transcribed and what is ignored. The different factors present in cells from birth to death are determined by the body and other cells in the vicinity.
For example, thyroid and pancreas form cellular growth hormones.Transcription factor directly affects the protein which is further helpful in the transcribed DNA, which makes it functional. Although, when cells squeeze together, it will also provide signal to other neighboring cells. Hence, the process of cell differentiation has numerous inputs and possible outcomes.
Conclusion :
Beginning with a thorough grasp of the nematode C. elegans, scientists have made significant progress in comprehending cell differentiation. As an adult female, this little worm-like creature contains 959 cells. They are relatively straightforward to track from the zygote to the adult due to their tiny number. Scientists have begun to unravel some of the complicated epigenetic mechanisms at work in cell differentiation by tracing their cell lineage. To put it another way, it’s not just about how much DNA a cell contains, but also about where and how that DNA is expressed.