Sequencing of a fetal genome from parental samples demonstrates how we have advanced in genetic analyses, but the title of a June 6 article in The New York Times, "DNA Blueprint for Fetus Built Using Tests of Parents," gives me pause. While the content does reflect a few interviews where researchers caution against overemphasizing what DNA sequences can tell us, the majority of the public reading the headline will see, yet again, an oversimplified and potentially damaging version of what we actually know about genetics.
Genes play an important role in our development and functioning, not as directors but as parts of a complex system. "Blueprints" is a poor way to describe genes. It is misleading to talk about genes as doing things by themselves. There are very few instances of direct gene-to-trait scenarios, even in well known "genetic" disorders. Traits emerge from the interactions of genes and a range of developmental and environmental influences, and similar DNA sequences often produce slightly different outcomes. Our DNA influences who we are, but not in a linear or easily described manner. (See here for more.)
DNA contains basic information that, when combined with the appropriate organic structures (in the egg) and context (the mother's uterus), will facilitate the growth of a single cell (the combined sperm and egg) into a multibillion-cell person. Note that I say "facilitate," not "determine." The DNA is not the blueprint of life; rather, it contains many of the basic codes and signals for the development of an organism. At its core DNA contains the basic information needed to assemble molecules called "proteins," which are the building blocks of our bodies, and it also acts to regulate how and where different proteins are made and used.
Genes contain information, but the actual relationship between genes and our bodies and behavior is complicated. Chemical interactions inside our cells, interactions between cells, and developmental processes above the level of DNA occur throughout the life span. Most one-gene-to-one-trait analogies are unrealistic. For example, although your hands are composed of numerous proteins that emerge from information in your DNA, hands themselves are not the product of a "hand gene." Hands are the product of a developmental program in which DNA plays an important, but not exclusive, role.
Think of genes as having many types of relationships with traits. Single genes can affect single molecules, groups of genes may work together to produce effects, and one gene can even have many effects on a number of different traits and/or systems. Most genes have many of these patterns at the same time. In all cases the same gene can produce slightly different proteins in different individuals.
Multiple factors influence the development of an organism. These include chemical and physical patterns, internal and external influences, and physical constraints on shape and size, in addition to the information carried in the genes. To make things even more complex, starting with the successful joining of sperm and egg, epigenetic (outside the DNA) processes also affect development. Changes in temperature, fluctuating chemical environments, and mistakes in chemical cues in addition to variations in DNA produce slightly different outcomes.
There is little evidence to support any one-to-one relationship between genes and behavior. However, DNA does influence our physical structures (brain, eyes, mouth, hands, and so on), and because behavior is exhibited via these structures, all behavior has some genetic component.
For example, you are reading this blog using your eyes (optical tissue, muscles, nerves) and maybe your hands (muscle, bones, tendons) to scan the letters and words on the page. You are also using your brain (a set of neurons, vascular tissues, and various hormones that connects all the organs in your body and mediates among them) to process the meaning. All of these elements have a genetic component. However, you are reading the words, a behavior that must be taught to you, and you are reading them in English, something else that must be taught to you. Do reading and using the English language have a genetic component? Yes, the neurons, eyes, muscles, and other parts of the body used in reading are composed of molecules initially coded for by DNA. Are there genes for reading in English? No, the specific language that someone reads is an experiential factor, as languages are parts of cultural systems. Can aspects of our genetic complement impact our ability to acquire specific reading skills? Possibly. Structural differences in the eyes, motor connectivity, and even hormone pathways in the brain might impact the pace and pattern of reading acquisition.
There is a very complex set of relationships between our bodies and behavior on the one hand, and DNA, development, and environment on the other. This relationship is not linear, nor can it be easily described as a simple equation. We should not use simple models or labels such as "blueprints," "building blocks," or "code of life" to describe DNA and genes. Rather, the DNA is an integral component of life itself, and understanding the function of genetic material is critical to understanding evolution and the functioning of organisms. But an understanding of genetics is by no means the complete picture.
For a better understanding of these topics, have a look at these sources:
Fox-Keller, E. The Mirage of a Space Between Nature and Nurture. Duke University Press (2010).
Fuentes, A. Race, Monogamy and Other Lies They Told You: Busting Myths About Human Nature. University of California Press (2012).
Robinson, T.R. Genetics for Dummies (2nd Ed.). Wiley Publishing (2010).
Originally it designated a modification of a gene or set of genes (alleles). This modification was such that it changed the phenotype of the owner of this new combination. But, we know now that subtle modifications of a wide range of genes in a same DNA sequence can lead to changes in phenotype and that these modifications are extremely slow.
The rate of change is in the order of several thousands to several millions of years. This is what makes the study of the genetic mechanism of evolution so difficult. This is compounded by the absence of DNA material in most fossils.
It would be interesting to read the author’s take on this subject.
Re: "...[H]ands are composed of numerous proteins that emerge from information in your DNA..."
What is the evolutionary explanation for the origin of the information in DNA?
As for the origin of RNA, and it's capacity to be both information, as well as to conduct chemical reactions (DNA can't do the latter), you need to turn to abiogenesis. This has not much to do with evolution any more. Evolution isn't the only theory science is based on.
Hope this helps.
For those who are interested in the study of Genetics, there is a good future for this discpline because there is still so much work to be done.
Until then....BULLOCKS!
One can apply the technical analogy quite well... but it has to be done correctly and not naively. What most people fail to learn, of course (because our schools are not teaching it right), is that DNA only expresses the building materials of cells. There is no detailed construction plan that says "this protein goes right HERE!". Once genes are expressed and the proteins are made, the biochemical machinery "assembles itself" (with help of said reproductive system), and that is indeed very different from a technical assembly process.
As for self-assembly... that's happening day in day out in every single one of your cells. It doesn't take a fertilized egg cell to do that, or a reproductive system. To make an embryo, though, does take a reproductive system that does a lot more things than just to "hold" it. You may want to read a book on the subject or two. Or ask any future mom.
:-)
DNA does NOT describe the whole animal before it is born. You take the same egg and sperm in identical women, and the individuals would NOT be the same when they are born. Even identical twins can be slightly different very early on...but their DNA is basically the same!
It is NOT a blueprint.....a better analogy would be its a "recipe"!
It does? It tells you how to make the sheet metal that the car is made of out of iron ore? It tells you how to build the microchip in the engine control out of sand?
Of course it doesn't. It only tells the people who are skilled in the art of making cars how to make this particular car. It still relies on the skill of these people and on everybody else who make the materials and parts the car is made of. If you were to amend the blueprints with ALL of the REQUIRED information, you would basically have to include the whole technological knowledge of mankind, including much of physics, chemistry etc..
"DNA does NOT describe the whole animal before it is born."
Indeed, no more and no less than the car blueprints define the whole manufacturing process. That's what I said... you can't be naive about the interpretation of these different, yet somewhat similar processes, when using the analogy.
"... and the individuals would NOT be the same when they are born."
Neither are any two cars identical when they are being manufactured. Nature, of course, strives for diversity, manufacturing strives for identity.
"It is NOT a blueprint.....a better analogy would be its a "recipe"!"
A recipe is a blueprint for the preparation of food... :-)
Because indeed chronological order matters, what one genes does in one stage of embryonic development, may be something completely different in another stage. And there is no one-to-one translation of step 1 to the taste of the cake (embryo), step 2 to the colour and step 3 to the consistency. Rather, all three steps, followed correctly, lead to the specific taste, colour and consistency of the cake.
There's nothing like an ingredient list in an organism's DNA. It eats what it can get, within the range of what it can live on.
But a program would be equally valid I suppose, though one might argue many programs easily crash when too many variables change.
It's all semantics, really. But thanks for the correction!
DNA, in fact, IS a blueprint, notwithstanding the fact that development is additionally affected by a variety of environmental factors.
A blueprint has a picture of the final product. A program (genetic or computer) has a set of instructions for how to assemble the final product. A single genetic mutation can result in a whole leg growing where a fruit fly's antenna would have been. To make that kind of change in a blueprint, you would have to erase the whole antenna and draw in the whole leg. You simply can't do it by changing only a single bit, the way you can in a program.