Our genes and their effects: Q/A part 2

 Here are some more questions from Leah that I am attempting to answer. Please read on if it interests you!

For a clearer idea, please refer to the post “Why Do We Age And What Can We Do To Stop It? AND “Why We Age? Q/A part 1″


1) How different is human genetics from plants in that we are able to quickly genetically modify plant organisms with immediate results; but as you say, human trait change takes a significant amount of time?

It has been found that though plants and humans have different genes, but the process of mutation is the same in the case of both. Since plants and animals evolved only because of stable mutations over many years; your question that we are able to genetically modify plants with immediate results lies here:

We generally use a virus that infects plants to carry a piece of foreign genome (fish gene/ antibiotic resistance gene etc etc) in to the plant. The virus has been weakened considerably, so it does not cause it’s usual infection in the host plant. But, owing to its nature, it takes over the host cell’s genetic machinery to make copies of itself and there by of the foreign gene as well, by integrating in to the genome of the host. There fore, its easier to manipulate plant genetic material. While manipulating human genes, the problems of ethics are more stringent. Plus if a virus is used to transport the correcting gene/ gene product in case of a diseased individual, there is no guarantee that the virus will not turn harmful again. And unless the new genes are directly added to the germ cells (reproductive cells and the mutation is stable), it will not be passed on to the kids.

2) Is it possible that human trait change is happening faster than we think, but in smaller less noticeable amounts that we only notice when we start to see higher frequencies of disease etc.? Could these complex interplays be the mutations, but, again, go unnoticed if we aren’t looking?

Not all mutations lead to disease occurrence. AND NOT ALL INCIDENCES OF DISEASE ARE LINKED TO MUTATIONS. Also, there might be many other reasons for phenotypic changes (physical expressions as a result of genes present). A recent study showed that, a country’s improvement in economy and general developmental conditions can cause an increase in height in the general population. This might be because of improved resource allocation as a whole. So, although the genes play an important part, their expression is modified/managed by the environmental interactions.

Also, sometimes, the mutated genes are recessive, ie, they are masked by their dominant normal counter-part but in their own way affect the organism. Since they are recessive, they cannot be easily identified because the dominant gene gives the phenotypic or the physical attributes and not the recessive gene (though in complex systems there is an interplay of a large number of genes before a character is exhibited). There fore, mutations do go unnoticed, until a physical form or manifestation is seen leading to its discovery and study.
3) As you stated, “How our genes express themselves is determined by external environments to a great degree.” Isn’t every new birth technically a mutation of the previous DNA, and wouldn’t the evolving markers if generation previously adapting to new environments offer a slightly different DNA to each subsequent offspring? For example, we see the physical change in chickens over the course of just a few (human) generations as they go from being free-range-raised with healthy diets to being raised in dark rooms with no air or movement. Isn’t it possible we are changing faster than we think? We (Americans, can’t speak globally) can see the difference in height, weight, bone density, etc. when comparing us to our ancestry just a hundred years ago. Thanks to our external environments, technology, and diet, we are seeing some weakening in some people, some increased susceptibility to disease, and some greater instances if mental illness.

Here in comes a process of natural selection, because nature selects or eliminates at a faster rate than would a stable mutation that has to be widespread. If the environment is changing too quick, (a century / 2 centuries or sometimes even sooner), natural selection comes in to play where in individuals who are resilient based on their genetic codes can survive better than the rest. The weakening in some individuals might eventually result in their not being able to produce offsprings or healthy offsprings. This is why quick habitat changes also endanger species of animals and birds who cannot adapt quickly to their changing environments, since evolution is a slow process. There fore they gradually die out.

Like you said, the weakening in bone density etc is more persistent now than before is due to the same fact, people don’t need to use muscular strength as much as they had to use earlier, since lifestyles are sedentary and our society as a whole dictates HOW we should live out our lives: drive to work, sit at a desk, drive back, etc etc.. is channeling our energy away from the development in the muscle to other areas like the brain or simply storing the excess energy in the body.

This is also the reason why the size of our jaws reduced and our skeletal structure changed when compared to our early ancestors. Since the time they didnt have to chew raw food, discovered fire and cooked their food, and build weapons, they could free up more time to “think”, there fore, the energy was diverted from the muscles towards the development of the brain. These slow changes were passed on to the progeny of the naturally selected (best suited in any given circumstance) individuals and caused a change in structure as a whole. That’s why there is also a great difference between the early groups of humans who diverged in developed in different terrains (island/ hot tropics/ cold temperatures etc etc) along with their progeny who walk the earth today.

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Take this situation for example, a group of people have been shipwrecked on an island. The island has limited resources and there is no way those people can ever leave the island.

This is actually true with the history of our coal reserves. Back when the earth had giant trees with very weak structures and superficial root systems yet enjoying a stable climate; when the climate suddenly began to change and gave rise to swamps and more moisture, these trees fell down and died. Then came up the age of smaller trees and bushes and the ones that had a sturdier structure and deeper roots.

4)Adjusting for things like the increased existence of disease in some places, are we in a kind of mutative transitional period wherein we will see humans eventually become resistant to cancers like we are more resistant to colds and flu for example?

Our cells are mutating all the time. There might be thousands of reasons in the environment or its just the incorrect base pairing of the nitrogenous bases in DNA. Now, with the help of an inbuilt machinery, the cells can repair the damage but sometimes damages are retained, and if some aggravating factors are present, it will disrupt the repair machinery and make the mutations accumulate. That’s what happens with age. The mutations build up and can lead to disease and cancers.

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Sometimes, The body may find a way to live with the mutation and still survive in a healthy manner, but it’s not a wide-spread occurrence. As it is, the reasons of complex diseases including cancers have more factors at play than one or two. Like I mentioned in the earlier post, a community that is completely immune to cancers and some other diseases, has a mutated growth hormone, ie, the body is stunted as a result but functions properly anyway. Since growth factor (their production and regulation) can lead to cancers, its difficult to say whether adapting to one condition or a set of conditions can help become resistant to the disease. Biological systems change all the time and their behaviour is unpredictable, so I guess its difficult to say for certain. This is also the reason why we shouldn’t completely rely on computational tools to give us a realistic view of the scenario. It’s open to experimentation, analysis and conclusion.

Please note: These questions are beyond the scope of a single post. But I hope I have managed to list out a few important points.


©2013-2015, The Idea Bucket. Written By Ananya.





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