Changing One's Characteristics
Location: Outside U.S.
Date: Winter 2012-2913
Is there a time in our life when we are able to influnce the physical traits we pass on? For example if a man trains to run faster, then his son does and his son etc, when do they make their contribution to the overall improvement of their line? 18years of age, 25 40?
Thanks for your question. In humans, the genes are in the gametes (egg and sperm cells) and the DNA is not easily able to be changed. In order to change physical traits, the DNA must change in some manner. Thus, running faster does not produce a change in DNA.
There are exceptions to the above statements. Some bacteria and other single-celled organisms have DNA which can be altered by environmental factors and this ability to change allows the organism to adapt to changing environments.
In a practical manner, the only way to change the physical traits that a human passes on would be to alter the DNA in the embryo. Of course, this is not practical or ethical.
I hope this helps answer your question. Please let me know if you have any other questions.
I was listening to an interview of Julian Lennon, the son of world famous Beatle John Lennon, the other day on the radio. He was asked if any of his Dad’s talent rubbed onto him, and he answered “no” and that he was extremely frustrated by that fact. Although not a statistically significant data point what this tells us is that just because your Dad is a fast runner, doesn’t necessarily mean that you will be a fast runner also.
But that is puzzling, because your DNA comes from your Father (and your Mother) and there should be a direct correlation between your characteristics and those of your parents, but such is not the case. Look at the variations between brothers and sisters (even twins) for another statistically insignificant proof. The reason for that is that although you have similar DNA/genes, some genes are active (expressed) and others are not (suppressed).
This puzzle has opened a new field of study in Biology called Epigenetics. It is a relatively new field that requires a whole lot of work to fully understand these mechanisms, but it suggests that a parent’s level of nutrition and emotional state defines the parent’s hormonal state that effects the mechanisms that activate/deactivate genes. The really amazing thing is that sometimes these effects are seen in third generation children.
The best book I can recommend is “The Epigenetic Revolution”, ISBN # 978-0-231-16116-9, by Nessa Carey and standby for a detailed immersion in micro-biology.
You can also discover more by typing “epigenetics” into the search engine athttp://www.google.com, and that will take you to (among other places):
I hope that you will be the one who will solve these mysteries during your adult career in micro-biology.
When I teach evolutionary biology in my bio classes, we always start with comparing Darwin's ideas to poor LaMarck. He is important because it shows that Darwin was not the first person to think of the idea of evolution (far from it, actually); instead, it is his ideas about the way evolution works that have withstood the test of time. However, we do now see that traits that are first seen in parents, can be passed on to their offspring. And we are not talking about hidden, recessive traits either. We very often study newly discovered phenomena in model organisms, and work out the mechanisms in simple organisms first before trying to figure them out in more complicated organisms. So what is happening here? Was LaMarck correct? No, not the way we thought, anyway. When you were a little teeny zygote (single cell) you started dividing to create the multicellular organism that you are today. Somewhere along the way, your cells started turning off genes permanently so you could become differentiated and your cells could take on special jobs. We now know that much of that is done by what is called methylation. Methyl groups are a carbon atom with 3 hydrogens attached. When they "sit" on a sequence of DNA, the gene in that region can't be read and is turned off. This type of change in gene expression is called "epigenetics" because the actual sequence of the DNA hasn't changed; this is "upon the genome".
So what does any of this have to do with your original question? Sometimes genes can become de-methylated, or those that aren't methylated can become so. There are substances that are environmental, or that are consumed that can change the methylation patterns of genes. If a gene becomes methylated or de-methylated in one's lifetime, it is possible that the methylation pattern can be passed on to the offspring.
LaMarck believed that evolution was driven by "felt needs" of the organism. Epigenetics is still a function of the environment, so no, LaMarckianism is still not a plausible explanation for evolutionary change. And it has nothing to do with the time of life that the changes take effect.
It is not clear whether or not non-genetic activity can be passed on to progeny. It would be difficult to isolate the cause and effect because the genetics and other factors are intertwined. There are “schools of thought” that propose that it is possible, but “proving it” is another problem. It is a good topic for a debate, but in the end, I don’t think the answer can be isolated.
This is an interesting question which has been posed many times by scientists and students alike. I recall in Bio 102, a student asking, Professor Ralph Hillman the question, “Does ontogeny (the development of embryos) recapitulate phylogeny (ORP)?” This phrase suggests that an organism’s development will take it through each of the adult stages of its evolutionary history, or its phylogeny making its ancestral history reviewable. Jokingly, Dr. Hillman suggested it may be vice-versa, which few if any of us understood.
While most developmental scientists believe that this is not the case in biology, it is possible, and we clearly see this demonstrated in language development. If we look at bacteria and virus’ to change from generation to generation as seen in bacterial and antiviral resistance to drugs, we tend to apply this to humans. Consider the lifecycle of a bacteria is quite short, and we can follow many generations in a matter of weeks. Human generations are, naturally much longer. Bacterial resistance is a result of mutations and adaptation. The bacteria are simpler organisms and lack some of the repair genes that are incorporated in the human genome. (check out http://en.wikipedia.org/wiki/Recapitulation_theory and http://evolution.berkeley.edu/evosite/evo101/IIIC6aOntogeny.shtml ).
Now to address your specific question; it is unlikely that any scientific evidence, physical or genetic points in that direction. There may be too many variables to prove it premise one way or another. Consider all the nutritional, medical, conditioning, life style, infectious, that surround that and I think you may see that as we progress in so many areas related to health and physical (i.e. training, design of running shoes, clothing etc.). We should get better in physical activities in successive generations. However, we cannot so far attribute it to “passing the better genes” to offspring. Now, genetic engineering of the germ line of an individual may be passed on (I believe it is not legal in any country I know of). Currently, I believe scientists may only effect the somatic cell line.
The advent of new technologies like NexGen sequencing may reveal some changes in genetic evolution in humans, but it will not tell us why, and it may not tell us that all “things” are improving. I cannot see the answer being definitely put forth. It remains a possibility but remote (in my opinion)
I may not have answered your question, but I hope it gave you something to ponder
Stephen R. Dunn
Ass't Professor of Medicine (ret.)
In principle, classical understandings of genetics would argue that our environment and activities do not affect the genetic heritage we pass on to our children. That is already determined by out genetics when we are born, and no changes to our environment will change the genetics of our children. To read up more on this, I would suggest you study the history of 'Lamarckism' and how it was largely supplanted by Darwin's theory of natural selection.
However, there are two caveats to this general rule:
The first caveat is that if your environment and activities cause mutations in your germ line cells (eggs and sperm), you can pass mutations on to your children. This is generally not a good thing, which is why we try to avoid mutagenic ('mutation causing') sources such as harmful radiation and certain toxic chemicals. This is also why pregnant women are encouraged to avoid 'teratogens', or chemicals that are known to cause developmental abnormalities.
The second caveat is much more complex and an area of intensive genetic research. This revolves around the new field of 'epigenetics', or inherited traits which are not determined by the genetic code. Put simply, our genetic code can be thought of as a specific sequence of the four DNA nucleotides: A, C, T, and G. Classically, it is only this sequence which determines our children's genetic inheritance. However, recent studies have found that the expression and activity of these genetic sequences is partly controlled by 'epigenetic' factors - chemical modifications to the DNA and its histone proteins that change the way the genes are read by the cell. Two major known epigenetic factors are methylation of DNA nucleotides directly and acetylation of histone proteins (the proteins that DNA in chromosomes is wrapped around).
What is interesting about these epigenetic factors is that while methylation and acetylation are passed on to one's children, they can indeed change during the course of your life through various environmental factors. Scientists have shown some early data in mammals (but not humans) suggesting that epigenetic factors can indeed be passed on to children (and even grandchildren) even after the stimulus that caused the original epigenetic changes is not present for the later generations. This is an ongoing field of exciting scientific research, but it does seem like some environmental factors and activities may affect the expression of one's genetic code, and in turn that of one's subsequent children.
Dr. Shimon Unterman
Click here to return to the Molecular Biology Archives
Update: November 2011