evolution question

[BH]

when we see a change in an animal or plant from generation to generation, a new body part or trait, how do we know if new genetic information has added to its gene sequence or whether the genetic information was always there to begin with and just manifested itself for some reason in one offspring?

 

[Loren Pechtel]

If it simply manifested in one offspring then there are still changes--something changed to switch it on.

 

[bilby]

when we see a change in an animal or plant from generation to generation, a new body part or trait, how do we know if new genetic information has added to its gene sequence or whether the genetic information was always there to begin with and just manifested itself for some reason in one offspring?

Mostly we don't.

Although in recent years it's become possible to sequence nucleic acids fairly quickly and cheaply, so if the funding and time are there to do it, a comparison between the genomes can be made, and the changes investigated.

My understanding is (and I am probably waaaay out of date, as I haven't been trying to keep up, and Molecular Biology has been moving very fast) that a lot of phenotypic change is epigenetic - that is, mediated not by the genetic material itself changing, but by changes in what genetic material is read.

Methylation was getting a lot of press a while back - a gene can be turned on or off by the removal or addition of methyl groups, without a change in the underlying sequence of base pairs.

Ultimately the answer to any question in biology, and certainly any question in molecular biology, is "it's more complicated than you think it's going to be, even after you take into account the fact that it's more complicated than you think it's going to be".

The popular narrative of a simple string of base pairs, in three base groups each coding for a specific amino acid, which is then assembled into a protein, with the changing of one base pair thereby having the potential to change the properties of the final protein, and thereby ultimately the phenotype of the individual in which that change occurs, is not untrue, but it's such a dramatic oversimplification of the hyper-complex reality that on a clear day, you can see 'untrue' from there, if you squint a little.

 

[Cheerful Charlie]

I suggest checking out Sandwalk occasionally. A science blog by Laurence Moran, professor emeritus of University Of Toronto. There is a lot of good science going on and a lot of bad science also. Moran is a hard nosed biochemist who digs into this. Epigenetics, junk DNA etc get examined critically. Plus well aimed kicks at sloppy science, sloppy science journals who should know better, and occasionally, creationists. Warning, Sandwalk can get quite technical.

 

[BH]

I'm really interested in this subject. can anyone here give me about ten book titles to start off reading?

 

[Cheerful Charlie]

What you are asking about is evo devo. Evolutionary development. Probably might be a good idea to start with an introductory college text book on that subject. Be warned. It is a vast field that some people have studied their entire lives and still do not know all the details.

https://www.quantamagazine.org/in-test-tubes-rna-molecules-evolve-into-a-tiny-ecosystem-20220505/

...
When researchers gave a genetic molecule the ability to replicate, it evolved over time into a complex network of “hosts” and “parasites” that both competed and cooperated to survive.
...

 

[Swammerdami]

The popular narrative of a simple string of base pairs, in three base groups each coding for a specific amino acid, which is then assembled into a protein, with the changing of one base pair thereby having the potential to change the properties of the final protein, and thereby ultimately the phenotype of the individual in which that change occurs, is not untrue, but it's such a dramatic oversimplification of the hyper-complex reality that on a clear day, you can see 'untrue' from there, if you squint a little.

For example,  RNA editing makes various changes to the RNA codons after the RNA has been transcribed from the DNA. This is one way eukaryotes' nuclear membrane is useful: the editing process is much slower than protein construction so keeping the RNA contained for the editing prevents premature translation.

In vertebrates, editing is rare.... In other organisms, such as squids, extensive editing (pan-editing) can occur; in some cases the majority of nucleotides in an mRNA sequence may result from editing.
. . . An example of C-to-U editing is with the apolipoprotein B gene in humans. Apo B100 is expressed in the liver and apo B48 is expressed in the intestines.

 

[Peez]

There is a great deal to sift through here. When we see a change in an organism (plant, animal, or any other), we do not typically see “a new body part”. Whether or not we see a new “trait” is going to depend on how that term is defined.

Quantifying “information” can be quite technical, and complex. That said, we can say that new information is generated by genetic mutation, and then increased in sexually-reproducing organisms by shuffling and mixing genes. This results in genetic variation in the population.

Some of this genetic variation contributes to variation in traits. Selection on these traits can then reduce variation in traits, and in genes.

That’s it. It is not a question of a mutation generating a trait in one offspring, rather it is selection (and drift) acting on variation in a population.

 

[Gun Nut]

when we see a change in an animal or plant from generation to generation, a new body part or trait, how do we know if new genetic information has added to its gene sequence or whether the genetic information was always there to begin with and just manifested itself for some reason in one offspring?

because we know how bodies know how to build body parts... through the blueprint that is the genetic code. so if a body is doing something new it is because the body is reading new instructions.
Edited to add in light of bilby's post..
.. reading new instructions because they're newly added instructions, or due to a change in the mechanism that reads the instructions that were already there... as in epigenes.

 

[bilby]

when we see a change in an animal or plant from generation to generation, a new body part or trait, how do we know if new genetic information has added to its gene sequence or whether the genetic information was always there to begin with and just manifested itself for some reason in one offspring?

because we know how bodies know how to build body parts... through the blueprint that is the genetic code. so if a body is doing something new it is because the body is reading new instructions.
Edited to add in light of bilby's post..
.. reading new instructions because they're newly added instructions, or due to a change in the mechanism that reads the instructions that were already there... as in epigenes.

Yeah, it's far more complicated than that. Genes aren't an instruction set or a blueprint for making a phenotype, and the influences on phenotype are myriad. Sure, genetics and epigenetics are a big-ish part of that, but there's a stack of other influences, which is why identical twins aren't identical.

Many developmental steps exhibit chaotic responses to apparently trivial environmental conditions, so that a tiny variation in conditions (from being on this side of the uterus, and not that side) result in very large differences in final appearance, form, or function.

Bilby's first law of biology applies: Every accurate statement about biology can be rendered even more accurate by adding "...but in reality, things are more complicated than that".

 

[Bomb#20]

Bilby's first law of biology applies: Every accurate statement about biology can be rendered even more accurate by adding "...but in reality, things are more complicated than that".

Your so-called "law" grossly underestimates biology's complexity.

 

[Swammerdami]

Genes aren't an instruction set or a blueprint for making a phenotype, and the influences on phenotype are myriad. Sure, genetics and epigenetics are a big-ish part of that, but there's a stack of other influences, which is why identical twins aren't identical.

I think you are underestimating the influence of DNA. Many of the "non-DNA" influences are themselves a result of genes. For example the RNA editings I mentioned upthread are controlled by special RNA's and proteins which are themselves transcribed or translated from the genome.

Identical twins ARE rather ... identical! Watch the Three Identical Strangers documentary. (It's an interesting story for reasons other than showing identical triplets to be very similar to each other. Do NOT abandon the film half-way through; that's when the big "plot twist" occurs!)

 

[bilby]

Genes aren't an instruction set or a blueprint for making a phenotype, and the influences on phenotype are myriad. Sure, genetics and epigenetics are a big-ish part of that, but there's a stack of other influences, which is why identical twins aren't identical.

I think you are underestimating the influence of DNA. Many of the "non-DNA" influences are themselves a result of genes. For example the RNA editings I mentioned upthread are controlled by special RNA's and proteins which are themselves transcribed or translated from the genome.

Identical twins ARE rather ... identical! Watch the Three Identical Strangers documentary. (It's an interesting story for reasons other than showing identical triplets to be very similar to each other. Do NOT abandon the film half-way through; that's when the big "plot twist" occurs!)

I think you are underestimating the influence of the environment.

Identical twins aren't identical. People who know them well can almost always tell them apart.

 

[Peez]

Genes aren't an instruction set or a blueprint for making a phenotype, and the influences on phenotype are myriad. Sure, genetics and epigenetics are a big-ish part of that, but there's a stack of other influences, which is why identical twins aren't identical.

I think you are underestimating the influence of DNA. Many of the "non-DNA" influences are themselves a result of genes. For example the RNA editings I mentioned upthread are controlled by special RNA's and proteins which are themselves transcribed or translated from the genome.

Identical twins ARE rather ... identical! Watch the Three Identical Strangers documentary. (It's an interesting story for reasons other than showing identical triplets to be very similar to each other. Do NOT abandon the film half-way through; that's when the big "plot twist" occurs!)

I have no doubt that bilby understands the role of DNA in directing the production of RNA. It would add that, as far as we can determine, epigenetic effects are limited and are themselves influenced by DNA. That said, bilby is correct that so-called identical twins are not actually identical. They are not even genetically identical (in fact different parts of your body are not genetically identical to each other), but they are even more different in their traits. I refer you to bilby's first law on biology.

 

[Swammerdami]

Wow. Obviously when I wrote "identical" this was whimsical shorthand for "ALMOST identical." Are you guys unusually pedantic? Or intent on pretending Swammerdami is an idiot?

I'll give you credit and assume you knew that "almost identical" was the intended meaning, but felt even this was an exaggeration. In that case you are simply wrong at least in some cases.

In the documentary I mentioned, the boys had very similar interests, very similar appearance, answered questions in unison, thought they were looking in a mirror, and so on. This despite that they (and their adoptive parents) were unaware they were triplets until they met by chance at age 19. And the adoptive parents were deliberately chosen to have very different income levels: this was part of a 'nature vs nurture' experiment.

I personally knew two identical twins whom very few people could tell apart. There is an amazing anecdote that proves they were almost indistinguishable; I won't recite it here because it is a very personal story with possible legal implications.

 

[bilby]

Wow. Obviously when I wrote "identical" this was whimsical shorthand for "ALMOST identical." Are you guys unusually pedantic? Or intent on pretending Swammerdami is an idiot?

I'll give you credit and assume you knew that "almost identical" was the intended meaning, but felt even this was an exaggeration. In that case you are simply wrong at least in some cases.

In the documentary I mentioned, the boys had very similar interests, very similar appearance, answered questions in unison, thought they were looking in a mirror, and so on. This despite that they (and their adoptive parents) were unaware they were triplets until they met by chance at age 19. And the adoptive parents were deliberately chosen to have very different income levels: this was part of a 'nature vs nurture' experiment.

I personally knew two identical twins whom very few people could tell apart. There is an amazing anecdote that proves they were almost indistinguishable; I won't recite it here because it is a very personal story with possible legal implications.

And such close similarity is the exception, not the rule.

So clearly genetics ain't everything.

 

[Jokodo]

Genes aren't an instruction set or a blueprint for making a phenotype, and the influences on phenotype are myriad. Sure, genetics and epigenetics are a big-ish part of that, but there's a stack of other influences, which is why identical twins aren't identical.

I think you are underestimating the influence of DNA. Many of the "non-DNA" influences are themselves a result of genes. For example the RNA editings I mentioned upthread are controlled by special RNA's and proteins which are themselves transcribed or translated from the genome.

Identical twins ARE rather ... identical! Watch the Three Identical Strangers documentary. (It's an interesting story for reasons other than showing identical triplets to be very similar to each other. Do NOT abandon the film half-way through; that's when the big "plot twist" occurs!)

I think you are underestimating the influence of the environment.

Identical twins aren't identical. People who know them well can almost always tell them apart.

Identical twins are identical mostly in their looks. There's this set of twins I know long enough that a hypothetical offspring of a hypothetical union between me and one of them would be allowed to vote and drink alcohol, and I've been close friends with half of it for the better part of that time. I still sometimes struggle to tell them apart in photos. As soon as you meet them in real life, all doubt is gone. They have different goals in life, different hobbies, different mannerisms, different ways to talk, walk, move. And they've lived together for most of their lives.

 

[Peez]

Wow. Obviously when I wrote "identical" this was whimsical shorthand for "ALMOST identical." Are you guys unusually pedantic? Or intent on pretending Swammerdami is an idiot?

I'll give you credit and assume you knew that "almost identical" was the intended meaning, but felt even this was an exaggeration. In that case you are simply wrong at least in some cases.

In the documentary I mentioned, the boys had very similar interests, very similar appearance, answered questions in unison, thought they were looking in a mirror, and so on. This despite that they (and their adoptive parents) were unaware they were triplets until they met by chance at age 19. And the adoptive parents were deliberately chosen to have very different income levels: this was part of a 'nature vs nurture' experiment.

I personally knew two identical twins whom very few people could tell apart. There is an amazing anecdote that proves they were almost indistinguishable; I won't recite it here because it is a very personal story with possible legal implications.

Please stop. The difference between "identical" and "almost identical" is not pedantic at all (particularly in this context: "identical twins aren't identical"... "Identical twins ARE rather ... identical!"). Why did you not think that bilby meant "almost identical"? Would you agree that all humans are genetically "almost identical" to each other (99.9% is almost 100%)? Do you understand how important the difference is between "almost identical" and "identical" in evolution?

 

[Swammerdami]

Please stop. The difference between "identical" and "almost identical" is not pedantic at all (particularly in this context: "identical twins aren't identical"... "Identical twins ARE rather ... identical!"). Why did you not think that bilby meant "almost identical"?

No, YOU stop. My writing "Identical twins are ... identical!" was obviously whimsy, intended to be slightly humorous. "Identical twins are ... similar!" would not have the same effect.

Obviously I use much different diction when I'm writing for submission to technical journals. But I don't plan on self-censoring here to cope with boring sophomoric pedantry.

As for why bilby did NOT mean "identical twins aren't almost identical" the question rather answers itself, no? Get a grip.

Would you agree that all humans are genetically "almost identical" to each other (99.9% is almost 100%)? Do you understand how important the difference is between "almost identical" and "identical" in evolution?[/I]

What??? What possible relevance does this have to a discussion of identical twins? If I indulged in sophomoric disingenuity I'd caricature this "argument" as "Neanderthal/Sapiens 99.7%. Identical twins 99.9+%. Same-same."

Weren't you the one who didn't understand the huge gulf between prokaryotes and eukaryotes? How does Professor Nick Lane's thinking compare with yours? Or are you just going to quibble that he begins a chapter by discussing cuckoo clocks?

 

[skepticalbip]

I know diddly-squat about biology but I think that I have gleaned from this thread that identical twins aren't.

 

[Bronzeage]

I'm really interested in this subject. can anyone here give me about ten book titles to start off reading?

Start with this guy:

 

[Peez]

Please stop. The difference between "identical" and "almost identical" is not pedantic at all (particularly in this context: "identical twins aren't identical"... "Identical twins ARE rather ... identical!"). Why did you not think that bilby meant "almost identical"?

No, YOU stop. My writing "Identical twins are ... identical!" was obviously whimsy, intended to be slightly humorous. "Identical twins are ... similar!" would not have the same effect.

Obviously I use much different diction when I'm writing for submission to technical journals. But I don't plan on self-censoring here to cope with boring sophomoric pedantry.

As for why bilby did NOT mean "identical twins aren't almost identical" the question rather answers itself, no? Get a grip.

Would you agree that all humans are genetically "almost identical" to each other (99.9% is almost 100%)? Do you understand how important the difference is between "almost identical" and "identical" in evolution?[/I]

What??? What possible relevance does this have to a discussion of identical twins? If I indulged in sophomoric disingenuity I'd caricature this "argument" as "Neanderthal/Sapiens 99.7%. Identical twins 99.9+%. Same-same."

Weren't you the one who didn't understand the huge gulf between prokaryotes and eukaryotes? How does Professor Nick Lane's thinking compare with yours? Or are you just going to quibble that he begins a chapter by discussing cuckoo clocks?

I will just point out that I have forgotten more about genetics, and the difference between prokaryotes and eukaryotes, than you have ever know. Have a nice day.

 

[ramoss]

Genes aren't an instruction set or a blueprint for making a phenotype, and the influences on phenotype are myriad. Sure, genetics and epigenetics are a big-ish part of that, but there's a stack of other influences, which is why identical twins aren't identical.

I think you are underestimating the influence of DNA. Many of the "non-DNA" influences are themselves a result of genes. For example the RNA editings I mentioned upthread are controlled by special RNA's and proteins which are themselves transcribed or translated from the genome.

Identical twins ARE rather ... identical! Watch the Three Identical Strangers documentary. (It's an interesting story for reasons other than showing identical triplets to be very similar to each other. Do NOT abandon the film half-way through; that's when the big "plot twist" occurs!)

I think you are underestimating the influence of the environment.

Identical twins aren't identical. People who know them well can almost always tell them apart.

Identical twins are identical mostly in their looks. There's this set of twins I know long enough that a hypothetical offspring of a hypothetical union between me and one of them would be allowed to vote and drink alcohol, and I've been close friends with half of it for the better part of that time. I still sometimes struggle to tell them apart in photos. As soon as you meet them in real life, all doubt is gone. They have different goals in life, different hobbies, different mannerisms, different ways to talk, walk, move. And they've lived together for most of their lives.

It is more likely that identical twins will have different goals/hobbies etc if they live together than if they grew up separately. There is the urge to be individuals, and that desire will cause them to purposely find divergent interests. Those that are brought up separately don't have the factor of needing to be different, so they can quite often be more alike.

 

[steve_bank]

I thought studies on twins separated at birth and raised in different families showed identical twins can have similar interestsand characteristics.

Twins - identical and fraternal - Better Health Channel

betterhealth.vic.gov.au

www.betterhealth.vic.gov.au

To form identical twins, one fertilised egg (ovum) splits and develops two babies with exactly the same genetic information. This differs from fraternal twins, where two eggs (ova) are fertilised by two sperm and produce two genetically unique children, who are no more alike than individual siblings born at different times. Twins are more or less equally likely to be female or male. Contrary to popular belief, the incidence of twins doesn’t skip generations.

Fertilisation​

Hormones secreted by the ovaries, and a small gland in the brain called the pituitary, control the menstrual cycle. The average cycle is around 28 days. After a menstrual period, rising levels of the hormone oestrogen help to thicken the lining of the womb (the endometrium) and release an egg from one of the ovaries (ovulation).

If the egg is fertilised on its journey down the fallopian tube, it lodges in the thickened womb lining, starts dividing and evolves into an embryo.

Identical or ‘monozygotic’ twins​

Around one in three sets of twins is identical. This occurs because the fertilised egg divides in two while it is still a tiny collection of cells. The self-contained halves then develop into two babies, with exactly the same genetic information.

Twins conceived from one egg and one sperm are called identical or ‘monozygotic’ (one-cell) twins. The biological mechanisms that prompt the single fertilised egg to split in two remain a mystery.

Approximately one quarter of identical twins are mirror images of each other, which means the right side of one child matches the left side of their twin.

Fraternal or ‘dizygotic’ twins​

Around two in three sets of twins are fraternal. Two separate eggs (ova) are fertilised by two separate sperm, resulting in fraternal or ‘dizygotic’ (two-cell) twins. These babies will be no more alike than siblings born at separate times. The babies can be either the same sex or different sexes, with the odds roughly equal for each.

 

[Swammerdami]

Did anyone hunt down and watch the Three Identical Strangers documentary? VERY interesting.

 

[Rhea]

Did anyone hunt down and watch the Three Identical Strangers documentary? VERY interesting.

It does sound interesting - but alrming when I read that the “parents were chosen,” because it implies the entire lives of these three people was an unwilling experiement…

I'm really interested in this subject. can anyone here give me about ten book titles to start off reading?

@BH
I really love the book, “Endless Forms Most Beautiful” by Sean Carroll regarding evolutionary development (evo devo). It gives great information on this and is written for thouse outside of the field. I won’t say “lay people” because I think you need a certain amount of science or math study to really catch all that he is saying.

Also, Carroll did several videos for the Howard hughes Medical Institute (HHMI) on traits that you can look up on the interwebs.

 

[Swammerdami]

Did anyone hunt down and watch the Three Identical Strangers documentary? VERY interesting.

It does sound interesting - but alrming when I read that the “parents were chosen,” because it implies the entire lives of these three people was an unwilling experiement…

Definitely. The first half of the documentary was a fun "feel good" story which I almost turned off — I already feel good!

But I kept going for a few minutes more and ... What The F**K!!!!

 

[Bomb#20]

I'm really interested in this subject. can anyone here give me about ten book titles to start off reading?

@BH
I really love the book, “Endless Forms Most Beautiful” by Sean Carroll regarding evolutionary development (evo devo). It gives great information on this and is written for thouse outside of the field. I won’t say “lay people” because I think you need a certain amount of science or math study to really catch all that he is saying.

Also, Carroll did several videos for the Howard hughes Medical Institute (HHMI) on traits that you can look up on the interwebs.

Seconded. Note that it's by Sean B. Carroll, the biologist, not Sean M. Carroll, the much more famous physicist. Sean B. Carroll is the better writer by a country mile.

 

[ramoss]

Did anyone hunt down and watch the Three Identical Strangers documentary? VERY interesting.

It does sound interesting - but alrming when I read that the “parents were chosen,” because it implies the entire lives of these three people was an unwilling experiement…

I'm really interested in this subject. can anyone here give me about ten book titles to start off reading?

@BH
I really love the book, “Endless Forms Most Beautiful” by Sean Carroll regarding evolutionary development (evo devo). It gives great information on this and is written for thouse outside of the field. I won’t say “lay people” because I think you need a certain amount of science or math study to really catch all that he is saying.

Also, Carroll did several videos for the Howard hughes Medical Institute (HHMI) on traits that you can look up on the interwebs.

The whole twin study by the Louise Wise adoption agency would be considered highly unethical these days. .. it was sketchy back then I think. What isn't mentioned is that some of the identical twins that were split were chosen because of mental health issues of the mother.