السؤال 114

A breed of dog has been produced by many generations of selective breeding. What has happened to the variation within that breed?

It has increased, because a new breed has appeared
It has decreased, because similar individuals have been bred togetherالإجابة الصحيحة
It is unchanged, because breeding does not affect variation
It has decreased, because the breeder removed alleles from the DNA

الشرح

Choosing parents that resemble each other narrows the set of alleles handed to the next generation, so the dogs of the breed end up more alike than the population they were drawn from. The appearance of a new breed looks like extra variety when breeds are compared with each other, but inside the breed the range of alleles is smaller than before. A breeder never alters the DNA itself; the alleles are simply not passed on when the individuals carrying them are not chosen as parents.

الشرح

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