4. Why do people have to be careful when breeding purebred doqs?

While quality breeders do test prospective parent dogs for defective genes -- and avoid breeding them if there are defects -- the broad problem of defects continues to grow as current breeding practices narrow the gene pool ever further. If you insist on a purebred puppy, then by all means, you should have one

a compound light microscope is used to magnify objects in steps.  

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