That's because our non coding region doesn't actually code for any protein. We do not use our noncoding region to synthesize any type of polypeptide chain. And so when we have a point mutation taking place on our non coding region, that will lead to a silent mutation. So a mutation in the non coding region will not cause negative effects because the non coding region is not actually used to synthesize our proteins. But what about a mutation that takes place on the coating region? So he said that sometimes a mutation can take place, a point mutation can take place on our coating region and still not actually cause any harmful effect.