The effect differs. It could produce a different amino acid in the sequence because the corresponding codon has changed. It could also prevent the production of the originally intended sequence by changing one of the amino acids of a "start" codon (aka AUG) or extend the protein's sequence by modifying a "stop" codon (UAA, UAG, UGA or UGG), producing a new protein that might be useless or have different effects on the cell.
Answer: b. reaction 3
Explanation: When an enzyme is present in a reaction acts as a catalyst, increasing velocity of reaction and decreasing the activation energy, when not present an enzyme the reaction velocity is very low and implies high activation energy, being unfavorable to the system
A Genetic cross also cross breeding is the deliberate breeding of two different individuals that results to offspring that carry part the genetic material of each parent. A monohybrid cross is the breeding of two organisms that differ in a single trait. A hybrid is an offspring from a cross between parents and has different phenotypes for a specific trait.