Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: ConfusedHermit on 24/01/2013 16:12:03

Title: What traits are passed on, genetically?
Post by: ConfusedHermit on 24/01/2013 16:12:03
Hermitís back! And Iím confused again! Well, more curious than anything ;{D~

Iíve been thinking about the wonders of how our DNA combinations make a new human(s) with traits from both, and wondering just how far this goes in less heard-of cases. Iíll just get right to my questions.

1.) A couple have a kid. Both of the mates have no thumbs, from an accident. Would their kid have thumbs? Or thumb problems? Would that be passed on?

2.) Same scenario, only both the mates have surgically added extra fingers to their hands. Would their kid have extra fingers? Or finger problems? Would that be passed on?

3.) A couple have a kid. Both of the mates got gene therapy so they gain a benefit/immunity internally. Would their kid have this as well? Would it be passed on?

3.) Same scenario, only both the matesí gene therapy did something that shows physically on their body. (Like purple polka-dots!) Would their kid have this as well? Would it be passed on?

I suppose the main/general question behind all of these comes back to the question in the title. We can lose and gain things internally and externally that arenít what we were born with. Is there ever a case where such things get passed on? Or will our offspring always turn out like we turned out as infants?
Title: Re: Will the result always be a human as we know them?
Post by: schneebfloob on 24/01/2013 20:24:35
The answer to 1&2 is no. This idea was put forward by Jean-Baptiste Lamarck, and was called Lamarckism or the inheritance of acquired characteristics. This is the idea that offspring would inherit characteristics acquired by the parents over the course of their lives e.g. the lost thumb or extra finger idea. This hypothesis was ultimately destroyed as we learnt more about genetics and how traits are passed on.

As for 3&4 it depends. It depends upon where and when the genetic modification took place in the parents. There are two broad types of cell in the body: somatic and germline. Germline cells are cells that go on to produce the gametes, whilst somatic cells are everything else. If the modification occurred within somatic cells then the answer is no. But, if a modification was induced within the germline then this modification would subsequently be passed on to all of the gametes produced by the parent and would be passed on to their offspring.

Title: Re: Will the result always be a human as we know them?
Post by: CliffordK on 24/01/2013 20:26:16
Obviously the answer to surgery is that the surgery is not transmitted in DNA.

Now, say you had no thumbs, and were trying to teach your "normal" child how to write with a pencil (with writing by example).  It is quite possible the child would learn to imitate the parent, and awkwardly hold the pencil.  However, part of childhood development is exploring the use of one's body, and I would assume many grips would be picked up and would be absolutely normal.  Handshakes, for example, would likely be normal.

Gene therapy is more complex.  As I understand it, the gonads are fairly well isolated, and it is quite possible that the new genes would not spontaneously enter the egg and sperm, so the mutation would not necessarily be passed on.  Likewise, the placenta offers a significant barrier from transmission of microbes to the infant.  The birth canal, however, can transmit microbes to the infant.

Keep in mind that most gene therapy delivery mechanisms involve the use of modified viruses.

The infant, of course, receives some of the maternal antibodies.  So, the first generation infant would have some of the immunity for the first several months, after which the immunity would wane, unless the infant is also exposed to the antigen.

Later generations of infants would not receive the grandmother's compliment of antibodies, unless the mother was also exposed to the antigens. 

Gene therapy carried out in an oocyte or blastocyst would likely get passed on to future generations.
Title: Re: Will the result always be a human as we know them?
Post by: cheryl j on 03/02/2013 21:47:40
While thumb surgery won't affect the thumbs of offspring, new theories in epi-genetics suggest that environmental factors can turn on or turn off genes and this effect can be transmitted to the next generation, sometimes several generations, although it tends to be diluted with each one. On a science program on the CBC yesterday, the example of this they described was that people exposed at an early age to famine were not only shorter and stockier, but their offspring were as well.