In gene therapy, a defective gene is replaced by a virus carrying a normal gene. If successful, 1. The cells divide and daughter cells express the normal gene.
2. The cells are recycled after death.
3. The cells lack a nucleus.
4. The cells do not produce the normal gene.

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meiosis is the first to occur after the nuclei of opposite of opposite mating types fuse

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.