Some changes in DNA occur naturally and lead to no harmful effects;

有些DNA的变化是自然发生的不会产生有害影响；

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Experiments have shown there to be no harmful effects from chronic exposure to acetylene at high concentrations.

实验显示慢性接触高浓度乙炔没有有害影响。

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Some changes in DNA occur naturally and lead to no harmful effects; these changes in a population are called polymorphisms.

有些DNA的变化是自然发生的不会产生有害影响；这些在一个群体中的变化被称为多态性。

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So it can be seen as having no harmful effects on the environment.

VOA: special.2009.10.05

Harris Perlman says the best part of the new treatment is that there were no harmful or major side effects.

VOA: special.2010.03.16

Second, Carraguard has shown no harmful effects in the early human trials.

ECONOMIST: HIV microbicides

The inventors of the technology say it does not affect any other marine life and has no known harmful effects on the shark or the wearer.

CNN: Divers embrace anti-shark device

She was prescribed an oral insulin medication -- a medicine that is no longer given to adolescents due to harmful side effects.

CNN: December 24, 2012 -- Updated 0455 GMT (1255 HKT)