Signal Transduction part 1 -

Where do babies come from?

Developmental biology is a field of study that attempts to answer this question with modern genetics. How is it that starting with one cell (the egg) following fertilization we become trillions of cells in hundreds of tissues that is us? Cells divide to form two cells (called daughter cells) and those two cells can be different from each other even though they both have exactly the same DNA. But the genes encoded by the DNA are not all similarly expressed. That is, not all the genes make RNA that in turn directs the production of proteins.

Following division the daughter cells have different genes making RNA and different proteins. It is largely proteins that make cells different from each other.

One can imagine early genetically determined fate decisions in cells that lead to tissue formation as a branching pattern of dominoes, a path with many forks. The first decision leads to two paths the next to four paths and so on. As the first domino falls it pushes over the next until a fork is reached. Our genes direct the domino (cell) down the correct of the two paths available for that particular cell. Similarly further down the path new forks require new decisions.

If something results in the domino to push down the wrong path (an endocrine disruption, for example) it can’t be recovered. The dominoes have already fallen. If the incorrect decision is made at the beginning then the entire pattern is messed up. If it occurs later after a number of correct decisions have been made then only smaller parts of the domino pattern are wrong.

What are those forking domino pathways and how do our genes force the correct decisions? Can environmental exposures force the wrong decisions?

Before we go into the details of developmental process we need to consider the machinery of the switches that send the dominoes down one fork or the other.

In Signal Transduction part 2, we’ll take a closer look at these switches.

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Originally published at lcresearchcenter.tumblr.com.