Question

Imagine you want to study one of the human crystallins, proteins present in the lens of the eye (see Figure 1.8). To obtain a sufficient amount of the protein of interest, you decide to clone the gene that codes for it. Assume you know the sequence of this gene. Explain how you would go about this.

Short answer

When the nucleotide sequence of a gene is known, this gene can be amplified by using a polymerase chain reaction that produces billions of copies of DNA in a few hours.

The primers can be taken that are complementary to the sequence of gene coding crystalline protein to attach the gene, and then many cycles of PCR can produce a large number of genes that will code for crystalline protein.

Step-by-step solution

Protein

Proteins are types of biomolecules formed after polymerization in amino acid molecules. All proteins variate in their sequence of amino acids that are coded by the DNA sequence of a gene. Their activity is added after the suitable post-translation modification in the cells.

Step 2:Crystallin

Crystallins are structural proteins in the lens of human eyes that are found outside of the lens. Two gene families are found that are alpha-crystallins and betagamma-crystallins. Alpha-crystallins work as chaperones that assist in proper protein interactions.

Step 3: Cloning of the crystalline gene

According to the given scenario, the sequence of the gene to be cloned is known. Thus, many copies of the gene are produced in the lab by using polymerase chain reaction, a technique used to amplify a gene and make billions of copies in a short duration.

A segment of the target gene sequence, Taq DNA polymerase, nucleotides, and primers that have complementary sequences of the target sequence are used in PCR reactions. Primers help to amplify the desired sequence by repeated cycles of denaturation, annealing, and extension in PCR.