What are some of the benefits of squeezing so much data into virtually every cell in the body? Why did we not evolve with one central repository of DNA rather than having it replicated throughout the body?
One of the benefits has to be that our genetic information cannot be lost simply by removing one part of the body. Could you imagine losing your arm to an injury and having all of your genetic information lost as well? Also if there was some sort of centralized DNA repository there would have to be some way to communicate that information to every cell in the body. There would also have to be some sort of mechanism to differentiate between cells to send the right information. Skin cells need to know how much pigment to excrete and liver cells need to know how much glucose to release into the blood during extended exercise. I guess one of the major benefits of cellular DNA vs repository DNA is that as long as all of our vital systems are intact we can survive because each cell holds the information it needs to keep on working.
Assume that the hereditary information carried in genes and DNA is responsible for a lot of the differences we observe in humans and other living things. How could just four different bases in DNA strands be responsible for the almost endless variety found in nature?
We only have 26 letters in our alphabet and look at what we can do: Shakespeare, The Odyssey, South Park… There are only 10 base numbers and look at what we can computer: the speed of light, the speed of sound, etc… See the complexity comes as more levels of the base pairs are added. I do not remember the exact equation, but it had something to do with multiplying the different variables (the base pairs) by the possible number of combinations. For instance, if we were just talking about one level of four variables, then there would be 16 different variations that could be completed just on that one level. As you get to the second level there are now of course 32 options, but you also have to factor in the order of the pairs of four so you would have to multiply 32 by 2 because there are two options for the order of the pairs. As you can see just going from one level to two brings us from 16 possibilities to 64 possibilities. The options increase exponentially. It is through this wide range of options that DNA can contain so much information.
I would also like to add that DNA is the single greatest barrier to the theory of evolution. When Darwin was alive they did not even know the internal structure of a cell, let alone the genetic blueprint. I have never seen any explanation for DNA as it pertains to evolution through natural selection that was more than speculation. The problem with DNA and evolution is that DNA has syntax, meaning a set of underlying rules that govern how the cell interprets the information. Kind of like our syntax for the English language. For instance, we have rules that govern how words work in a sentence and how punctuation defines the sentence. It is the same for DNA. I have never heard a single scientific explanation for how the syntax of DNA developed and I probably never will.
Pruitt, N. L., & Underwood, L. S. (2006). Bioinquiry: Making connections in biology (3rd ed.). Hoboken, NJ: John Wiley & Sons, Inc.