Lactase Synthesis Lab Report

Introduction On average Americans eat 627 lbs. of dairy products each year (“USDA ERS - Dairy Data,” n.d.). When consumed the principle carbohydrate in dairy, lactose a disaccharide sugar, is either digested in the small intestine by lactase or is passed to the large intestine where it is broken down by bacteria. The lactose disaccharide is composed of the monosaccharides glucose and galactose. Lactase in an enzyme that catalyzes the breakdown of lactose into its two monosaccharides in a hydrolysis reaction so they can be absorbed through the intestinal mucosa membrane (Olds & Sibley, 2003). For the majority of mammals, lactase activity is significantly reduced after being weaned from their mother’s milk. Since most mammals do not continue
The mutation investigated in this experiment that is associated with lactase persistence is the located upstream of the LCT gene. In this mutation a single nucleotide polymorphism changes a cytosine into a thymine that then can be detected using the polymerase chain reaction technique (Biology 225 lab manual, S2017). In this experiment amplification Refractory Mutation System PCR was used to detect this nucleotide change. Two primers were used in two different PCR reactions, one to detect the wild type allele and the other to detect the mutant allele. These primers are allele specific so the mutant type primer has the reverse complement of the single nucleotide polymorphism responsible for lactase persistence and the wild type primer has the reverse compliment of the gene responsible for lactase non-persistence (Biology 225 lab manual, S2017). Lactase persistence is a dominant mutation, but only about 30% of the world’s population is lactase persistent, these people are typically from Northern Europe, and parts of Africa and Asia where people have been consuming dairy for millennia. The other 70% of the world’s population is lactase non-persistent which is the recessive wild-type allele (Biology 225 lab manual, S2017). The objective of this experiment is to determine the predicted phenotype of lactase persistence or lactase non-persistence of all biology 225 lab students and compare their predicted phenotype to
The percent of students who self- reported to be lactose tolerant was 74.02%, and the percent who self-reported to be lactose intolerant was 25.8%. The percent of subjects whose predicted phenotype matched their self-reported phenotype of either lactose tolerance or intolerance was 65%. Variations in predicted phenotype and self-reported phenotype could result from other mutations in the DNA that could cause lactase persistence or non-persistence other than the single nucleotide polymorphism tested for in this experiment or another chemical component in dairy that they cannot digest could cause them to exhibit symptoms of lactose