Explain the benefits of making human therapeutic proteins, such as insulin, using recombinant DNA technology.
Calcitonin is a small protein hormone made up of $32$ amino acids. One of its roles is to suppress the activity of cells known as osteoclasts, which break down bone tissue. Calcitonin has been used as a therapeutic protein to treat osteoporosis. In osteoporosis, excessive breakdown of bone tissue in older people results in lower bone density and a greater risk of fractures. Fig. 3.1 displays the amino acid sequences of human calcitonin and calcitonin from the salmon fish, $\textit{Salmo salar}$.
The two amino acid sequences shown in Fig. 3.1 may be compared. The amino acids that occupy the same position in both sequences can be counted and then expressed as a percentage of the total number of amino acids in one sequence. This is known as percentage sequence similarity. Use Fig. 3.1 to calculate the percentage sequence similarity of human and salmon calcitonin. Show your working.
Compared with human calcitonin, salmon calcitonin is more biologically active. It stays active in the human body for a longer time and binds to calcitonin receptors more easily. Bioinformatics was used to identify this more biologically active form of calcitonin for the treatment of osteoporosis. Explain how bioinformatics helped identify salmon calcitonin as a suitable form of calcitonin to treat human osteoporosis.
Use Fig. 3.1 to work out the percentage sequence similarity between human and salmon calcitonin. Show your working.
Relative to human calcitonin, salmon calcitonin is more biologically active. It remains in the human body for longer and attaches to calcitonin receptors more readily. Bioinformatics was used to identify this more biologically active form of calcitonin for treating osteoporosis. Explain how bioinformatics helped identify salmon calcitonin as a suitable form of calcitonin to treat human osteoporosis.
Name an enzyme that can: • cleave plasmid DNA • link the salmon calcitonin gene to plasmid DNA.
Identify and explain two plasmid properties that make them suitable as vectors in gene cloning.
The gene coding for salmon calcitonin is introduced into bacteria in a specially designed plasmid called an expression vector. An expression vector must include a prokaryotic promoter, such as the $lac$ promoter. Explain why differences in the control of gene expression in prokaryotes and eukaryotes mean that expression vector plasmids have to contain a prokaryotic promoter.