The correct answer is cocaine. Cocaine is a strong recreational drug which acts as a stimulant by increasing one's alertness, attention and energy. Since cocaine targets the reward system of the brain, chronic exposure to this addictive substance can cause adaptation of the system and development of tolerance. Development of tolerance leads to the gradual increase of dose, which can lead to irritability, restlessness, confusion and paranoia. Chronic use will also alter the neurological signalling of pain and hunger, which leads to chronic itching and aches and an increased need to eat.
Answer: Only a single codon in the gene sequence is changed in base substitution mutation. Although a base substitution alters only a single codon in a gene, it can still have a significant impact on protein production.
