Selective breeding for new traits?

[spider_creations]

I know Kermit was selective breeding bigger and black ghost pretty cool right 

 

[Andrea]

I think that, until we know more about the why and how, we should not tinker too much DNA-wise. Sure, you get nice colours, a bigger animal...but what about possible negative traits hitchhiking on those desired traits? You'll have a bright pink 8 inch mantis which is unable to molt, for instance. Or is very aggressive to males..

The golden retriever was bred for colour and sweet disposition. But what traveled along with it? Hip dysplasia. Cancer.