-A high school student from Tennessee
January 29, 2018
The really short answer is that scientists don’t change the DNA itself. The egg has the stuff it needs to read the parts of the DNA instructions necessary to make an embryo.
The egg can “open up” or “unroll” the parts of the DNA needed to get the egg to start on the journey towards developing into a baby. To do this, it uses something in the egg called “pioneer factors.”
Different Cells Use Different Parts of the Same DNA
DNA is Rolled Up in Proteins
Obviously, our genes aren’t paper wrapped around a stick. However, the truth isn’t too far off. The DNA that makes up a gene is wrapped around individual proteins called histones.
Remember the individual instructions in the DNA called genes? Well, they don’t do anything as DNA.
Instead the instructions are read by the cell and ultimately turned into proteins. It is these proteins that do the work in a cell.
Histones are one of these proteins. They are the “spool” around which DNA is wound.
However, some transcription factors, the “pioneer factors” can actually open up the DNA. Yes, scientists really call them pioneer factors.
Like the pioneers of the old west, they find where they need to go all on their own, settle down, and other factors come to them. Pioneer factors push the histones out of the way so the other proteins can read the DNA.
Eggs are Full of Pioneer Factors
Before eggs are fertilized, their DNA isn’t being read. Mom gave the egg all the proteins it would need to start going from one cell to a full organism.