Can the genetics be modified in such a way that a person's sexual orientation

[tarekatpf]

Can the genes or their epigenetic switches be modified in such a way that a person's sexual orientation changes, and the change becomes inheritable?

Hypothetically, if a genetically exclusively heterosexual male performs sexual activity with another male in the absence of a female partner to obtain sexual pleasure, can the genes/ epigenetic switches of the first male be modified in such a way that (A) He will be sexually attracted predominantly towards other men from then on, and (B) If he mates with a female in future and produce an offspring male, the male child will be genetically predominantly homosexual? By "an exclusively heterosexual male", I meant the kind of male who's sexually attracted exclusively towards female and wouldn't engage in sex with a male if there is no adverse condition/ restriction on him. ( For example, a lot of homosexual men in Asia have to marry women due to social pressures. )

Also, I know we don't know yet if somebody's sexuality is purely genetic, but that's why I said hypothetically. I want to understand if life events could influence genetics if sexuality was purely genetic. In other words, can purely genetic traits be altered by life events?

Thank you for your attention.

 

[Pythagorean]

Well, first, let's talk about homosexuality as a spectrum. Some are more homosexual than others.

Now, let's consider development. Many of the traits that are associated with brain structure are a result of development, so it may be that giving a straight adult male a handful of "gay genes" (genes associated with homosexuality) does nothing since the brain has already developed - but if you would have swapped the genes earlier in development, it may have led towards homosexual tendencies.

Of course, this ignores social effects, which are most likely tangled in nonlinear ways with genetics. Someone who "naturally" may have a neutral attraction stance (such as as "queer" or "pansexual") might come to be disgusted by homosexual acts if they are raised in a household where homosexuality is shamed - or they may be a defiant individual who acts out against moral standards set out by their family and community; now, we're considering intrinsic traits that don't have any direct relationship to homosexuality - that is, how malleable someone is to social expectations.

So you can see, it gets complicated pretty quickly between considering intrinsic biological traits (attraction and personality dispositions) which can be genetic and/or developmental, and how they interact with social pressures.

 

[Ygggdrasil]

Also, I know we don't know yet if somebody's sexuality is purely genetic, but that's why I said hypothetically. I want to understand if life events could influence genetics if sexuality was purely genetic. In other words, can purely genetic traits be altered by life events?

Life events do not influence genetics. The idea that behaviors learned by an individual can be passed down to one's children (a theory known as "Lamarckism") has been disproven by modern genetics. Traits and behaviors acquired by an individual do not create any heritable changes in one's DNA sequence.

In some organisms, however, environmental factors may cause heritable changes in an individual without altering the DNA sequence. These traits, known as epigenetic traits, are thought to be mediated by changes in the DNA and histone modifications associated with a gene. However, nearly all of these modifications are reset during animal embryogenesis, so scientists do not think that many traits can be inherited epigenetically in humans. This question, however, still requires further research before we can have a clear answer.

 

[HizzleT]

Just to build on Ygggdrasil's post, this is a very interesting paper demonstrating transgenerational epigenetics:

Hackett, Jamie A., et al. "Germline DNA demethylation dynamics and imprint erasure through 5-hydroxymethylcytosine." Science 339.6118 (2013): 448-452.
(http://www.sciencemag.org/content/339/6118/448).

My understanding of genetics is not as robust as might be, but if transgenerational epigenetics is a real occurrence, then it would appear conceivable that it could act to perturb natural selection, resulting in a change in gene frequency as a function of time. Moreover, it would make sense for such mechanisms to be selected for. Perhaps my understanding is flawed however.

I think it would make more sense to look in the brain to see what is different between heterosexual and homosexual people and try and work backwards from there. That said, the computational geneticists out there might be inclined to disagree!

Lastly, at the risk of sounding very boring, let me say: nature vs. nurture is not a real debate! It's both. Saying something is 30% nurture and 70% nature explains n-o-t-h-i-n-g. Literally meaningless information.

 

[Evo]

Life events do not influence genetics. The idea that behaviors learned by an individual can be passed down to one's children (a theory known as "Lamarckism") has been disproven by modern genetics. Traits and behaviors acquired by an individual do not create any heritable changes in one's DNA sequence.

In some organisms, however, environmental factors may cause heritable changes in an individual without altering the DNA sequence. These traits, known as epigenetic traits, are thought to be mediated by changes in the DNA and histone modifications associated with a gene. However, nearly all of these modifications are reset during animal embryogenesis, so scientists do not think that many traits can be inherited epigenetically in humans. This question, however, still requires further research before we can have a clear answer.

This is a great place to close. Thank you Ygggdrasil.