making miniature animals big again

[BenTheMan]

Ok, so this idea came to me the other night when I was...in an altered state of mind.

So, we have miniature greyhounds:

which ostensibly came from regular greyhounds:

Basically, you breed the smallest greyhounds puppies you can find, and eventually you get smaller and smaller greyhounds---i.e. you're just "distilling" the smallness.

So what happens if you go the other way? Suppose I take a bunch of miniature greyhounds, and select the biggest puppies. Then I breed all of the biggest puppies for several generations.

Do I get big greyhounds back? And if so, do they have all the same characteristics of the original greyhounds from whence they came? I mean, since the "small" was recessive, may it be tied to a bunch of other recessive things? So when I get the big greyhounds back, they all have epilepsy or something?

I think, deep down, I have a desire to have a 150 lb chihuahua.

 

[cosmictraveler]

But then they wouldn't be the same at all as when they were "normal" sized. You now have a totally different animal than when you started both in size and in character.

 

[spidergoat]

It's possible, but they won't have the same genetic diversity as the originals.

 

[BenTheMan]

But then they wouldn't be the same at all as when they were "normal" sized. You now have a totally different animal than when you started both in size and in character.

Is this true?

I'd imagine that the genetic differences between small greyhounds and large greyhounds are pretty minimal, right? That is, a miniature greyhound is more similar to a regular sized greyhound than to a beagle or something?

 

[clusteringflux]

I have a desire to have a 150 lb chihuahua.

Are you sure about that?

 

[Hercules Rockefeller]

So what happens if you go the other way? Suppose I take a bunch of miniature greyhounds, and select the biggest puppies. Then I breed all of the biggest puppies for several generations.Do I get big greyhounds back?

It would be theoretically possible to reproduce the “original” greyhound, but not probable. Prolonged selective inbreeding to produce bizarre new dog breeds reduces genetic diversity, as already mentioned. Allele frequencies are gradually fixed and deleterious recessive alleles are uncovered. This results in a host of congenital defects. More selective inbreeding the other way will only further introduce such problems. Sterility would probably stymie the attempt before you got there.

But then they wouldn't be the same at all as when they were "normal" sized. You now have a totally different animal than when you started both in size and in character.

Is this true?

No, it’s not true. Selective breeding means just that – it’s selective. You select what traits you breed for and keep, and what ones you don’t keep. So you get pretty much what you want at the other end, in this case a dog that looks the same as an ‘original’ greyhound (assuming you could ever get that far).

 

[cosmictraveler]

No, it’s not true. Selective breeding means just that – it’s selective. You select what traits you breed for and keep, and what ones you don’t keep. So you get pretty much what you want at the other end, in this case a dog that looks the same as an ‘original’ greyhound (assuming you could ever get that far).

So a 150 pound greyhound could run as fast as a 40 pound one? A 150 pound one won't have the same disposition of a 40 pound one either I don't think.

 

[Hercules Rockefeller]

So a 150 pound greyhound could run as fast as a 40 pound one?

No, I was not trying to say that.

We may be talking about different things. I interpreted your statement as meaning that if Ben tried to selectively breed the miniature greyhound back to its original size, as he described in the OP, the resulting ‘restored’ greyhound would not look like the ‘original’ greyhound before it was bred to be miniature. I do not think this is necessarily correct.