Detection of A1/A2 genes using Sanger sequencing
One of the high nutrient-rich foods consumed by the human population is milk. This popular dietary choice is a staple food for most countries. Sources of milk vary ranging from an animal such as cows, goats, etc to other non-animal sources such as almonds, coconut, etc. With the recent focus been shifted towards the development of much healthier choices of milk options such as A1 and A2, the consumer provides different options for milk products such as in the form of liquid, or powder. Manufacturers have even successfully produced infant formulas. However, understanding the differences between both types of milk is important to making a healthier decision for life.
Milk contains a lot of essential proteins of which the majority (around 80%) is the protein “casein”. Of all the several forms of casein, the common forms are the A1 and the A2. As the name goes, A1 milk is associated with the A1 protein while A2 milk contains the A2 protein. Out of the two types of milk, the common and the most abundant is the A1 milk. The source of A1 milk is mostly from the cow breeds from Northern Europe, while A2 milk is from the cow breeds from southern France. While A2 milk is associated with several health benefits which have led to its increased production.
A1 and A2 proteins are almost identical with a protein length of 209 amino acids. Although highly identical, a single amino acid difference occurs which is at the 67th position in the protein chain. The amino acid residue in A1 protein is a histidine which is replaced by a proline residue in A2 protein. The potential of milk production often depends on the type or breed of cows used. To gather information as to whether the cow produces A1 or A2 milk, typing of the cow's DNA is carried out. This is done through the hair, blood, etc of the cow. The type of milk production depends on the type of beta-casein gene present in the cow. There are only two possible copies of the beta-casein gene in a cow which can be either A2A2, A1A2, or A1A1. Production of both the alleles A1 and A2 are in equal proportion and hence they follow the process of codominance.