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Given that all cells in a multicellular organism contain the same DNA (ignoring random mutations during mitosis), how does any given cell know what purpose it is supposed to have within an organism.

For example, how does a cell know to become a muscle cell, a neuron or a liver cell?

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closed as too broad by canadianer, David, Alan Boyd, AMR, Chris May 24 '17 at 21:12

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ As this is a very shallow question, I've voted to close. Search the topic "epigenetic regulation", and you will find your answer. If anything specific about this topic confuses you, please open a new question and we will be happy to help. $\endgroup$ – Bob May 23 '17 at 22:06
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    $\begingroup$ Your question is basically answered in a full semester course in Developmental Biology. It is far to broad for this forum. Suffice it to say it has to do with chemokine gradients and signaling producing differential translation in the cells of a developing multicellular organism. $\endgroup$ – AMR May 24 '17 at 17:39
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The answer to this question can be split into two parts: cell differentiation from stem cells and simple mitosis. Also, the answer I am providing mainly only applies to species that sexually reproduce.

During the primary stages of growth, immediately following the fertilisation of the female gamete, the zygote begins to divide. Most of these initial cells will not be specialised, they will be stem cells and these have the potential to asymmeterically divide. When they do this, each of the daughter cells will have a specific specialisation path to follow. Which path they will follow, muscular, neural etc. is determined by transcription proteins.

Once the stem cells have produced the correct daughter cells, the general structure of the organism will begin to take form. Once this happens and the cells have followed their development paths until they hit their final specialisation, mitosis takes over. This means that a muscle cell will divide, causing the organism to grow. A muscle cell, will only ever divide into a muscle cell, the same goes for all specialised cells. This is how an organism grows and maintains itself.

However, some stem cells do remain after the organism has matured. For instance, a mature neuron is unable to undergo mitosis, so stem cells are needed to allow for the production of new neurons to replace those that die, to take one example.

You can find out more here.

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  • $\begingroup$ But how is specific path recognized ? Arent the stem cell equiped with the same transcription proteins and DNA ? I assume for each type of cells there are different genes, how they will evolve, but the stem cell must be told which genes are to be translated. $\endgroup$ – Marvin May 23 '17 at 22:49
  • $\begingroup$ @Marvin Cell fate is controlled by intercellular signalling. A lot is not well characterized. See this answer: biology.stackexchange.com/a/24022/6307 $\endgroup$ – canadianer May 23 '17 at 23:14
  • $\begingroup$ But yet, the signalling toggles the dna demethylation and histone modification, which changes genes promotors. So two same stem cells with different fate dont have same intracrine hormones at the begining ? $\endgroup$ – Marvin May 23 '17 at 23:20

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