If an organism is homozygous for a particular trait, the organism a. has extra alleles on both chromosomes in a chromosome pair. b. is missing alleles on the chromosomes in a chromosome pair. c. has different alleles on the chromosomes in a chromosome pair. d. has the same allele on both chromosomes in a chromosome pair.

If an organism has two copies of the same allele, for example AA or aa, it is homozygous for that trait. If the organism has one copy of two different alleles, for example Aa, it is heterozygous.

the answer to your question is tooth decay.

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.