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Questions about Evolution?
- Thread starter painted wolf
- Start date
painted wolf
Grey Muzzle
LOL... I love that vid! :jiggy:
wa:do
wa:do
Autodidact
Intentionally Blank
Hey, are we supposed to be watching this space for an explanation of the role of HOX genes?
painted wolf
Grey Muzzle
ok, I've been asked to explain HOX genes and their role in evolution.
HOX (short for homeobox) genes are regulatory genes that control the location and development of major structures such as legs, eyes and hearts.
Because these genes are so vital to the building of an organism, they are highly conserved. (that is, mutations are actively selected against in these areas and thus they don't tend to change much over time)
This means that the same Hox gene that codes for a mouse eye, is essentially the same gene that codes for the eye of a fly.
This means you can take the Hox gene for the eye of a mouse and put it into a fly and get a working fly eye. (you don't get a mouse eye, because the Hox gene is a master switch to the other genes needed to make an eye)
Where evolutionary change comes into play is in how Hox genes are switched on and off during embryonic develpment, and how many copies of a particular Hox gene you use.
Hox, like all other genes, are in every cell of your body... but you don't have eyes all over the place. During development Hox genes are carefully switched on and off along the geography of the embryo.
I'll use the fly as an example of what happens when you mess with the Hox gene for eye devolopment (in arthropods this gene is called "eyeless" or ey for short, it is very nearly identical to the mouse version called "small eyes" or sey or Pax6 for short.).
If a mutation turns off eyeless in the fly, then you get a fly with no eyes.... simple enough.
If you turn on eyeless someplace else, say on the region of the body that will grow wings... you will end up with fully formed (but useless) eyes on the wings of the fly.
When you see a baby animal that has extra legs, this is because the Hox for leg development has been switched on in an area that it should not have been.
A lot of major evolutionary changes come down to the adding or removing of copies of Hox genes. This is most clearly seen in arthropods. Six legs, six areas where the leg Hox gene is turned on... but in Centipedes you keep adding new body segments and expressing the leg Hox gene on them (express the Hox for legs twice each segment and you get a Millipede.)
well, that is what you get off the top of my head... if you have any particular questions I'll see what I can do to fill in any blanks I've left.
wa:do
HOX (short for homeobox) genes are regulatory genes that control the location and development of major structures such as legs, eyes and hearts.
Because these genes are so vital to the building of an organism, they are highly conserved. (that is, mutations are actively selected against in these areas and thus they don't tend to change much over time)
This means that the same Hox gene that codes for a mouse eye, is essentially the same gene that codes for the eye of a fly.
This means you can take the Hox gene for the eye of a mouse and put it into a fly and get a working fly eye. (you don't get a mouse eye, because the Hox gene is a master switch to the other genes needed to make an eye)
Where evolutionary change comes into play is in how Hox genes are switched on and off during embryonic develpment, and how many copies of a particular Hox gene you use.
Hox, like all other genes, are in every cell of your body... but you don't have eyes all over the place. During development Hox genes are carefully switched on and off along the geography of the embryo.
I'll use the fly as an example of what happens when you mess with the Hox gene for eye devolopment (in arthropods this gene is called "eyeless" or ey for short, it is very nearly identical to the mouse version called "small eyes" or sey or Pax6 for short.).
If a mutation turns off eyeless in the fly, then you get a fly with no eyes.... simple enough.
If you turn on eyeless someplace else, say on the region of the body that will grow wings... you will end up with fully formed (but useless) eyes on the wings of the fly.
When you see a baby animal that has extra legs, this is because the Hox for leg development has been switched on in an area that it should not have been.
A lot of major evolutionary changes come down to the adding or removing of copies of Hox genes. This is most clearly seen in arthropods. Six legs, six areas where the leg Hox gene is turned on... but in Centipedes you keep adding new body segments and expressing the leg Hox gene on them (express the Hox for legs twice each segment and you get a Millipede.)
well, that is what you get off the top of my head... if you have any particular questions I'll see what I can do to fill in any blanks I've left.
wa:do
DarkSun
:eltiT
Alceste
Vagabond
Wow - you can get a technicolor fully illustrated chart of genetic variations off the top of your head? You are impressive!
Let me think of a question... OK, I remember something from that Life of Mammals documentary about whales still having vestigial hip bones. Isn't that bizarre?
Ha - not much of a question, really. I'd be interested in anything that pops into your head on the topic of vestigial traits though. Like, your top ten personal favourite bizarre vestigial traits.
painted wolf
Grey Muzzle
well, you know when I do graduate next year I'll have degrees in both Biology and Art.
Some even have tiny leg bones!
Hip bones are not that odd to keep, they do help anchor muscles used in reproduction (at least in those species that have them). The femur and occasional tibia bones however are totally useless... and sometimes entirely missing from one individual to another.
This is actually a bit tough. I'm going to add a couple of atavisms because I think they are really cool and show genetic vestigial traits that can be activated. I wanted to add a few that most people likely didn't know about, or give much thought to.
Well, whale hips are obviously on the list. (wicked cool was the atavistic dolphin that had hind flippers!)
Humans tails. (atavistic tails are even cooler! )
Wing of the kiwi (it's such a cute little thing)
Mammary tissue in male mammals. (double points for when males lactate!)
Pseudocopulation in female only lizard species.
The flesh covered eyes of cave/burrowing animals like cave fish and mole rats.
Crab tails... (at least in the ones that are not related to hermit crabs)
Human gene that no-longer codes for Vitamin C. (we have it as a pseudogene, but most other mammals can make their own vitamin C)
Horses born with extra toes (this is an atavism, but it's cool when it happens)
Platypus teeth (they develop in the embryo then are reabsorbed before birth)
wa:do
If the classification of a new species is done in the belief that none can no longer breed wit another part of the species, there should be evidence for this in isolated human cultures....eg some of them developing th inability to produce offspring with the general world population, any evidence of this?
rojse
RF Addict
Current humans today are one species, Eddy. In spite of vastly different appearances, we all have quite similar DNA.
"It's what is inside that counts" is not merely a trite expression.
painted wolf
Grey Muzzle
No human population has ever been that isolated from the rest of humanity for that long. Human generations are rather long and we love to travel... This means that while some minor changes phenotypically happened, but nothing so large as to produce a new species has.
wa:do
Autodidact
Intentionally Blank
Your conclusion doesn't follow. Just because evolution happens, it does not follow that a new species must have already evolved from Homo sapiens sapiens. However, we do know that Homo sapiens evolved from earlier pre-hominid species.
painted wolf
Grey Muzzle
As a species we really haven't been around that long.
wa:do
wa:do
Autodidact
Intentionally Blank
So painted, and thanks, great stuff. To cut this down to the six-year old level, where I live, what I get from all of this is that there are a lot of genes that work by turning other genes off and on, right? So that helps explain how evolution of certain traits proceeds faster than you might think. Like say e.g., not that this has happened or not, but a 2-winged creature could become a 4-winged creature, because the HoX genes would only have to mutate to say: "Grow another couple of wings right here," and in not-that-many-mutations, you get 4 wings. Or like a mole's foot bones are short, I imagine, while a bat's wings are long, and the HoX genes regulate this just by saying, "Start growing now; stop growing now" at different points, right?
So HoX genes really help explain the specifics of how organisms evolve?
And also tend to reinforce our common ancestry? Cuz the same gene makes a fly foot as a mouse foot, even though the feet are totally different?
And also they're really cool?
So HoX genes really help explain the specifics of how organisms evolve?
And also tend to reinforce our common ancestry? Cuz the same gene makes a fly foot as a mouse foot, even though the feet are totally different?
And also they're really cool?
painted wolf
Grey Muzzle
Basically... the extra wings thing can take more mutations if you want any functionality...
But the change from rodent like legs to bat wings isn't that difficult.
You keep the genes for bone growth switched on for extra long and you don't switch on the Hox gene that is responsible for killing off the skin between the digits.
They go a long way to explain the genetics behind evolutionary development.
Absolutely... either that or God is very lazy.
Totally cool!
wa:do
So if evolution happens then why cant we see it happening this way?
DarkSun
:eltiT
themadhair
Well-Known Member
We do. You are genetically different than your parents (the average being 175 new genetic mutations). Your children will be genetically different to you. Given enough time those genetic differences add up to great change.
painted wolf
Grey Muzzle
The human gene pool is too well mixed.
We see evolution happening in other places... the squirrels of the grand canyon for example... those on the north end are quickly becoming another species from those on the south.
It's also happening with the Indonesian population of elephants (should they not be hunted to extinction). Just to name two examples.
wa:do
Autodidact
Intentionally Blank
We can. It is. You have to look around you. New species are constantly evolving.
"A" can become "a" , this is "change" , now if I started out with a theory regarding the evolution of letters due to shapes , sounds etc ,lets call it the "abc theory" , now every time my theory was challenged I could mention that it can be seen happening by showing the different forms of the letters, "Look my abc theory can be seen happening in all the literature of the world" ...because I started of with the premise of one letter,or part of it being able to evolve into a new one, and people bought into it as it seemed obvious.