Ed Hypothesis about Coat Color

[aggle-rithm]

I have a hypothesis I've been thinking about recently. I saw an episode of the TV series Life on primates the other day, and it showed a species of monkey whose infants are brightly colored to allow the mothers to easily find them. As they mature, the coats turn a more drab color to make them less visible to predators.

I wondered if there might be practical relationship in canids between two traits that appear to be carried on the same gene: Docility, and colorful coats. I know that this relationship has been shown to exist in foxes as well as wolves/dogs, and it occured to me that these species might share a common ancestor for whom this trait was useful.

If a proto-canid relied more on vision and less on smell than their descendants do, then perhaps it would have been an advantage for their young to have spots or splotches to make them more visible to their mothers. It could also serve as a signal to adults that this is a baby, so it should be given some leeway.*

As the proto-canid matured, the gene that gave the infant both docility AND the colorful coat would be turned off, and it would become a drab, aggressive adult.

My hypothesis is that this gene still exists in canids today. In wild canids, it is permanantly switched off, while in dogs, it is permanently switched on.

Any obvious flaws in this idea?



*Today's dogs have "puppy breath" which signals adults, through smell, that the puppy shouldn't be treated too harshly for social transgressions. Or so I've heard.

 

[aggle-rithm]

Stand down, spelling Nazis. I realize I left the "o" out of "Hypothesis".

 

[blutoski]

I have a hypothesis I've been thinking about recently. I saw an episode of the TV series Life on primates the other day, and it showed a species of monkey whose infants are brightly colored to allow the mothers to easily find them. As they mature, the coats turn a more drab color to make them less visible to predators.

I wondered if there might be practical relationship in canids between two traits that appear to be carried on the same gene: Docility, and colorful coats. I know that this relationship has been shown to exist in foxes as well as wolves/dogs, and it occured to me that these species might share a common ancestor for whom this trait was useful.

If a proto-canid relied more on vision and less on smell than their descendants do, then perhaps it would have been an advantage for their young to have spots or splotches to make them more visible to their mothers. It could also serve as a signal to adults that this is a baby, so it should be given some leeway.*

As the proto-canid matured, the gene that gave the infant both docility AND the colorful coat would be turned off, and it would become a drab, aggressive adult.

My hypothesis is that this gene still exists in canids today. In wild canids, it is permanantly switched off, while in dogs, it is permanently switched on.

Any obvious flaws in this idea?

One: there's no way that there's one gene locus responsible for these two traits.

It's probable that the genes are what's called 'linked' - meaning they're physically close to one another on the chromosome. (a human example is freckles and red hair)

There's no reason to believe the traits have to have been selected together.
Just that when one is selected for, it selects for the other at the same time.

In fact: gene linkage has a dark side. Selecting for some desireable traits means you're also selecting for their neighbours. This has led to some breeds being known for their congenital disorders.

See: [Genetics of canid skeletal variation: Size and shape of the pelvis]

 

[aggle-rithm]

There's no reason to believe the traits have to have been selected together.
Just that when one is selected for, it selects for the other at the same time.

???

What's the difference?

In fact: gene linkage has a dark side. Selecting for some desireable traits means you're also selecting for their neighbours. This has led to some breeds being known for their congenital disorders.

I'm aware of the disorders associated with purebreds, which is one reason I have believed that a single gene carries more than one trait.

In fact, the way I've heard it explained is that a single gene can code for more than one protein. Was that incorrect?

Or is the definition of the word "gene" as controversial as "species"?

 

[LibraryLady]

Stand down, spelling Nazis. I realize I left the "o" out of "Hypothesis".

Would you like me to fix it?

 

[Professor Yaffle]

There's a section on selection of juvenile characteristics (neoteny) in dogs here:

http://en.wikipedia.org/wiki/Origin..._in_the_rapid_evolution_of_diverse_dog_breeds

 

[casebro]

Don't I hear that skin color in Humans takes seven genes?

Maybe one is near the nose-width gene,
One near the hair-straightness gene,
One near the precession gene,
One near the eye color gene,
One near the hair gene,
One near the IQ gene,
One near the fat location gene.

Maybe?

 

[Roboramma]

One: there's no way that there's one gene locus responsible for these two traits.

Why not?

 

[aggle-rithm]

Would you like me to fix it?

What will it cost me?

 

[William Parcher]

I have a hypothesis I've been thinking about recently. I saw an episode of the TV series Life on primates the other day, and it showed a species of monkey whose infants are brightly colored to allow the mothers to easily find them. As they mature, the coats turn a more drab color to make them less visible to predators.

How was it determined that the reason for the bright infant coloration is for easy finding? What about all the other monkey species which do not have brightly colored infants... do they lose their babies?

 

[aggle-rithm]

Why not?

This brings up an interesting question: Is our understanding of the word "gene" the same, now that we can actually look at the molecular structure of a gene, as it was when it was first coined?

Or did it once refer only to outward characteristics, and now refers to a length of DNA that encodes a single protein?

 

[aggle-rithm]

How was it determined that the reason for the bright infant coloration is for easy finding? What about all the other monkey species which do not have brightly colored infants... do they lose their babies?

Oprah said it was so, so it must be!

 

[William Parcher]

Maybe it's a way to force mothers to be extra protective against predators. I have to keep very close tabs on my baby because he was born day-glo orange. Might as well have an "Eat Me" sign pinned to his back.

 

[LibraryLady]

What will it cost me?

That depends. (see above)

 

[aggle-rithm]

Maybe it's a way to force mothers to be extra protective against predators. I have to keep very close tabs on my baby because he was born day-glo orange. Might as well have an "Eat Me" sign pinned to his back.

Or as I mentioned earlier, maybe it's a signal to adults in the group to give the kid a pass. He's not mature yet, so can't be expected to understand all the niceties of monkey society.

Or, it's the monkey equivalent of a "baby on board" sign.

 

[William Parcher]

Why isn't this found in other monkey species?

 

[aggle-rithm]

That depends. (see above)

Can you also correct my wildly inaccurate scientific claims?

 

[aggle-rithm]

Why isn't this found in other monkey species?

Who's to say it isn't? Just not by me, because I've done almost no research.

 

[blutoski]

???

What's the difference?

Semantics, apparently.

What I'm saying is that there is no reason to believe that a particular feature has been selected for to begin with.

So: the current parsimonious approach is to assume that a feature without obvious benefit was probably obtained accidentally through selection of a beneficial neighbour.

It's important to understand that artificial selection is directed against the whole animal. Genes may be culled even though they were not intentionally selected against.

I'm aware of the disorders associated with purebreds, which is one reason I have believed that a single gene carries more than one trait.

That's unlikely considering they appear to affect very different systems.
Gene linkage should be the parsimonious explanation.

In fact, the way I've heard it explained is that a single gene can code for more than one protein. Was that incorrect?

It's very rare. You may be thinking of multiple exons per gene, which are common. The gene can produce multiple amino acid chains, which combine into a protein.

Also common: multiple genes contribute to one protein. For example: the hemoglobin protein has three subunits spread across genes on two chromosomes. More complicated is that its heme cofactor is not produced in these genes, but is the product of perhaps a dozen more enzymes in a pathway. (I'm a little rusty on my biochem)

Point is: a typical protein has multiple genes, rather than a typical gene producing multiple proteins.

Or is the definition of the word "gene" as controversial as "species"?

Not that I'm aware of, no: "A locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions, and or other functional sequence regions."

The definition is not much help on a webforum discussion, I admit.



Another reason I suspect that a 'one gene for both traits' model is unlikely is that docility really comes across as a complex property.

My feeling is that this suggests multiple genes for that property alone.

 

[blutoski]

Why not?

It would be an incredibly unlikely combination of events.

* gene codes two proteins (rare but not impossible) or
* single protein controls two unrelated systems (rare but not impossible)
* both features are single-gene (really hard to believe)