Question

A mutation in the gene for a particular protein gives rise to the disease osteogenesis imperfecta.

Answer (and explain) the following five questions in one sentence each.

1. What is the name of the protein?

2. What is the mutation in this protein?

3. Describe the structure of this protein.

4. Why does this mutation disrupt the structure of the protein?

5. Will taking extra Vitamin C help cure osteogeneis imperfect? Why or why not?

Answer 1

1, the gene that codes for Collagen type-I protein gives rise to the disease osteogenesis imperfecta.

2, Substitution mutation or sometimes missense mutation in the amino acid sequence of the collagen protein is the reason for osteogenesis imperfecta.The glycine residue in the amino acid sequence is substituted by some amino acids with heavier or complex side chains in the triple helical structure of the collagen resulting in bone deformity- bone brittleness.

3, Collagen is a triple helical structure with alpha-1 and alpha-2 chains. The alpha-1 chain is identical whereas alpha-2 chains differ inthe amino acid composition. The amino acid such as glycine, proline and hydroxyproline is mostly present in the collagen structure.Every thirs residue in the helix is glycine. The structure is stabilised by hydrogen bonding and covalent crosslinks. The triple helical stucture is stabilised by steric repulsions between proline.

4, The substitution of glycine which is the simplest amino acid by some complex amino acids causes the collagen to bulge which is improper for the bone structure. this results in improper formation of triplex helix structure showing variation in the physiochemical property of the collagen structure.  

4, No, extra Vitamin-C will not help in curing osteogenesis imperfecta. Eventhough vitamin-C aids in formation of collagen, it cannot help in reversing the defects of collagen as it is due to the mutation in the gene.