Genetics or molecular biology advice for fiction writing - post any questions here

[Ray McCarthy]

I suppose if you lived in a regime where anyone with blue eyes was shot at the age of five for example it would be a good reason to

Though eyes can be dyed darker? maybe that's only the white though and not the iris.

 

[Ed Ryder]

Possibly, it was just a random example for why you might want to change eye colour in the first place and not just use contacts
s/blue/brown

 

[JoGunnar]

Thanks for your detailed answers. I didn't realize just to change eye color there are multiple things you would have to edit. Seems like a lot of work for something so small. But I guess that's how tech and medicine is. Things start out clunky and get more efficient and common place over time. Your answers are super helpful but also formed more questions for me, haha. For example...if a gene was editted would there be any way it could lapse back into the original version (say blue eyes turning back to the "natural" brown)? Can editted genes be controlled by medication or something like that?
This is my new favorite thread btw!

 

[Ed Ryder]

Usually if you change a gene it tends to stay changed, especially if it's a significant change, but there is a possibility that a single base mutation could naturally revert back to its original form though, but it's probably fairly slim: good old Wikipedia: Mutation - Wikipedia, the free encyclopedia . There's also the possibility of a different mutation happening naturally in the same gene which reverts its function. http://www.jacionline.org/article/S0091-6749(15)00800-3/abstract

Can edited genes be controlled by medication or something like that?

I guess they could, although it would be tricky if you are replacing a gene directly as you'd have to engineer a switch at the same time. Certainly not impossible though.
A real world example would be the use of the chemical tamoxifen (or Cortexiphan as I call it, being a Fringe fan!) to control the expression of an artificial transgene that causes DNA recombination between two sites in the genome (the Cre-LoxP system), so you can knock genes in a controlled manner. One could envision something where one drug would switch a gene off and a different one would turn it back on again.

 

[JoGunnar]

Thank you! This helps a lot. I have another question which may fall under your expertise, I can't seem to find an answer online. I'm working on a story that involves in vitro fertilization and was wondering if the frozen eggs they keep ever expire or degrade over time. It seems unlikely that they would stay viable indefinitely.

 

[Ed Ryder]

At least 12 years apparently! Twin delivery following 12 years of human embryo cryopreservation: Case report
In mice, stored embryos have been successfully resuscitated after 20 years of storage in liquid nitrogen, and cow sperm has been viable after 37 years of storage. Although it's impossible to test much further than that currently, it's predicted that they should remain viable almost indefinitely. This does raise ethical concerns for some people, especially if they believe life begins at conception.

This of course depends on a few things:
An available source of liquid nitrogen. Storage tanks are 'leaky' by design and have to be topped up regularly
Radiation. A study showed that mouse embryos can survive at least 2000 years of background radiation, but if that level is much higher (eg nuclear war etc) then they would need to be protected.
Cost. Storing embryos is really expensive, and freezing plus proper resuscitation is a highly skilled job

 

[Dave]

Usually if you change a gene it tends to stay changed, especially if it's a significant change, but there is a possibility that a single base mutation could naturally revert back to its original form though, but it's probably fairly slim.

Different genes mutate at different rates though. (This something I actually know about from genetic genealogy. The rates of change can be considerably different. Measuring this natural change can allow you to estimate when the mutation took place and therefore how long ago populations separated and how closely individuals are related to each other.) And yes, genes that mutated can mutate back again. As Ed says, mutations are extremely rare though, the system is designed to make very good copies. Environmental factors can increase the rate, as I'm sure you are aware. And as I'm also sure you are aware, most mutations are not important as most genes are junk anyway.

At least 12 years apparently! ...Storing embryos is really expensive, and freezing plus proper resuscitation is a highly skilled job

I read a report in a Newspaper last week (but despite searching online I can't find a link, sorry) about a scientist claiming that IVF is unsafe as none of the children have lived long enough for us to tell if they or their offspring will have any genetic problems, or if keeping the embryos longer will increase the chance of problems. As you might expect, this viewpoint has obviously caused quite a stir and most scientists disagree with it. There are no known safety issues, however, in essence they are correct; you can never say with certainty that something will never happen or something is safe, you can only say that it hasn't so far, or that it is safe, as far as we know.

 

[Ed Ryder]

Yes there's a massive difference between 'unsafe', 'we don't have any meaningful data either way' and 'I cherry-picked some data which supported my hypothesis and ignored all the rest'.

Original story and response here (presuming that's the one you meant!)
IVF an 'evolutionary' experiment, scientist warns
Claims IVF as dangerous to evolution as junk food 'grotesque': IVF expert

I don't know if his findings have been peer-reviewed and published though.
Then again he might be correct about issues with age - we'll know in half a century or so...

 

[JoGunnar]

At least 12 years apparently! Twin delivery following 12 years of human embryo cryopreservation: Case report
In mice, stored embryos have been successfully resuscitated after 20 years of storage in liquid nitrogen, and cow sperm has been viable after 37 years of storage. Although it's impossible to test much further than that currently, it's predicted that they should remain viable almost indefinitely. This does raise ethical concerns for some people, especially if they believe life begins at conception.

This of course depends on a few things:
An available source of liquid nitrogen. Storage tanks are 'leaky' by design and have to be topped up regularly
Radiation. A study showed that mouse embryos can survive at least 2000 years of background radiation, but if that level is much higher (eg nuclear war etc) then they would need to be protected.
Cost. Storing embryos is really expensive, and freezing plus proper resuscitation is a highly skilled job

Thanks for the article link. There's a lot of technical jargon that I didn't quite understand, but the parts I did were helpful. It's strange how the cells in the embryos don't degrade or get damaged from the liquid nitrogen like other cells (adult cells I guess).