Which of the following is not a major function of proteins in the human body and instead is mainly the role of nucleic acids such as DNA and RNA?

Introduction / Context:
Proteins are one of the major classes of biomolecules and perform a wide range of essential functions in living organisms. However, not every important biological function is carried out by proteins. Some roles are mainly performed by other molecules, such as nucleic acids or lipids. Exam questions often ask you to identify which function does not primarily belong to proteins, in order to check your understanding of the distinct roles of proteins and nucleic acids.

Given Data / Assumptions:

• The options mention building tissues, fighting disease, nail formation, and storing and transmitting heredity.
• We assume standard textbook descriptions of proteins as structural, functional, and regulatory molecules.
• We also assume basic knowledge that DNA and RNA are nucleic acids responsible for genetic information.
• The question asks which listed function is not a major function of proteins.

Concept / Approach:
Proteins serve many roles: they form structural components like collagen and keratin, act as enzymes that catalyse reactions, function as antibodies in the immune system, and serve as transporters and hormones. Hair and nails are largely composed of keratin, a fibrous protein. However, storing and transmitting hereditary information is primarily the job of nucleic acids, especially DNA, with RNA playing key roles in expression of that information. While proteins interact with DNA and help regulate genes, they do not themselves store the genetic code. Therefore, the function that does not primarily belong to proteins is the storage and transmission of heredity.

Step-by-Step Solution:
Step 1: Evaluate building and repairing tissues. Structural proteins such as collagen in connective tissue and actin and myosin in muscle clearly show that proteins help build and repair tissues. Step 2: Evaluate helping to fight disease. Antibodies are special proteins produced by the immune system to recognise and neutralise pathogens, so this is a key protein function. Step 3: Evaluate nail formation. Nails, hair, and the outer layer of skin contain keratin, a tough structural protein, so proteins contribute directly to nail formation. Step 4: Evaluate storing and transmitting hereditary information. The genetic code is carried by DNA and, to some extent, RNA. These are nucleic acids, not proteins, even though protein molecules may assist in packaging or expression. Step 5: Conclude that the only option not representing a primary function of proteins is the storage and transmission of heredity.

Verification / Alternative check:
Biology textbooks usually divide biomolecules into carbohydrates, lipids, proteins, and nucleic acids. Under nucleic acids, they state clearly that DNA stores genetic information and passes it to the next generation, while RNA helps in protein synthesis. Under proteins, they list roles such as enzymes, hormones, structural components, and antibodies. Genetic storage is never listed as a primary protein function. This clear separation supports the conclusion that heredity storage belongs to nucleic acids, not proteins.

Why Other Options Are Wrong:
Building and repairing tissues is a classic protein function, so option A cannot be the correct answer. Helping to fight disease is also a major protein role because antibodies and many immune system molecules are proteins. Contributing to the formation and structure of hair and nails is another protein function, as these structures are mainly made of keratin. These three options therefore represent genuine functions of proteins and are not the ones the question is asking for.

Common Pitfalls:
A common pitfall is to overlook the specialised role of nucleic acids and assume that any major life process, including heredity, must involve proteins. Another mistake is to think that because proteins bind DNA and regulate genes, they must store genetic information. In reality, while proteins play supportive roles in gene expression, the actual hereditary instructions are encoded in the nucleotide sequence of DNA. Remembering this distinction will help you confidently identify storage and transmission of heredity as the function that does not primarily belong to proteins.

Final Answer:
The correct choice is Storing and transmitting hereditary information from one generation to the next, because this role belongs mainly to nucleic acids such as DNA and RNA rather than to proteins.