Genes located on the same locus but having different expressions are

A. Multiple alleles

B. Oncogenes

C. Polygenes

D. Codominants

• Gene: A sequence of nucleotides that encodes for the synthesis of a product such as RNA or protein.
• Locus: A fixed position on a chromosome marked by a specific genetic marker.
• Expression: The functional outcome of a gene — the trait or product it encodes.

Options Explained

Option A: Multiple Alleles

• When more than two allelic forms exist for the same gene at a given locus, they are called multiple alleles.
• Example: Different alleles at the same locus may result in varied expressions of a trait.

Option B: Oncogenes

• Genes that have the potential to cause cancer.
• Mutations or abnormal activation lead to high expression, resulting in uncontrolled cell growth or tumors.

Option C: Polygenes

• Genes that individually have a very small or negligible effect on the phenotype.
• However, when multiple polygenes act together, they significantly influence traits such as skin color or height.

Option D: Codominance

• A condition where both alleles of a gene are expressed simultaneously, without one being dominant over the other.
• Example: Blood group AB in humans.

Final Answer

Option A: Multiple Alleles