At the molecular level, genes are specific segments of which type of biological polymer within the cell?

Introduction / Context:
Genes are the fundamental units of heredity that carry information from one generation to the next. To understand genetics, it is essential to know what physical substance actually encodes this information. This question asks you to identify the type of biological polymer that makes up genes at the molecular level.

Given Data / Assumptions:

• The question refers to genes as structures within cells.
• We are asked what genes are made of in terms of biological molecules.
• Options include nucleotides in nucleic acids, proteins, carbohydrates, fats, and mineral salts.
• We assume the standard model where DNA is the primary genetic material in most organisms.

Concept / Approach:
Genes are specific sequences of nucleotides in DNA (and in some viruses, RNA) that contain instructions for building proteins or functional RNA molecules. DNA, or deoxyribonucleic acid, is a polymer made from repeating nucleotide units, each composed of a sugar, phosphate group, and nitrogenous base. The order of these bases along the DNA strand encodes genetic information. Proteins, carbohydrates, and lipids play important roles in cell structure and function but are not the primary carriers of hereditary information in standard organisms.

Step-by-Step Solution:
Step 1: Recognise that genes are stretches of DNA on chromosomes in the nucleus of eukaryotic cells. Step 2: Recall that DNA is a nucleic acid built from repeating nucleotide units. Step 3: Remember that each nucleotide contains a sugar, a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine in DNA). Step 4: Understand that the sequence of these bases along the DNA chain is what encodes genetic information. Step 5: Note that proteins are made from amino acids and are the products or effectors of gene expression, not the genes themselves. Step 6: Conclude that genes are segments of nucleic acids, specifically polymers of nucleotides.

Verification / Alternative check:
Genetics and molecular biology texts clearly state that genes are located in DNA. Experiments such as the Avery, MacLeod, and McCarty transformation studies and the Hershey Chase bacteriophage experiments demonstrated that DNA, not protein, is the genetic material in many organisms. DNA structure models show it as a long polynucleotide chain, reinforcing that nucleotides are the fundamental units making up genes.

Why Other Options Are Wrong:
Proteins built from amino acids: Proteins are the products encoded by genes, not the genetic material itself in most organisms. Carbohydrates composed of sugars: These form structural polysaccharides and energy stores, not genes. Fats and other lipids: Important for membranes and energy storage but do not encode genetic information. Mineral salts and inorganic ions: Essential for cell function but not organised into gene sequences.

Common Pitfalls:
A common confusion is to think of proteins as genes because proteins determine traits like eye color or blood type. In reality, genes are the DNA instructions, and proteins are the outcomes of reading those instructions. To avoid error, remember the simple chain: nucleotides form DNA, DNA contains genes, and genes code for proteins.

Final Answer:
Genes are made of nucleic acids, which are polymers of nucleotides in DNA or RNA.