Different alternative forms of the same gene that occupy the same position on homologous chromosomes are called what in genetics?

Introduction / Context:
Genetics uses specific terms to describe how traits are inherited. This question focuses on the name given to different versions of the same gene that can lead to variations in a trait, such as different eye colours or blood groups. Knowing the correct terminology is essential for understanding Mendelian inheritance and more advanced genetics questions.

Given Data / Assumptions:

• We are talking about the same gene located at the same locus on homologous chromosomes.
• The question refers to different forms or variants of this gene.
• We assume basic knowledge of terms like gene, chromosome, and trait.

Concept / Approach:
A gene is a segment of DNA that codes for a specific trait. However, the DNA sequence of that gene can vary slightly between individuals, creating different versions. These versions are called alleles. For example, a gene controlling flower colour may have a red allele and a white allele. The combination of alleles that an individual has is called its genotype, while the physical expression is called the phenotype.

Step-by-Step Solution:
Step 1: Identify the key phrase in the question, which is "different forms of genes". Step 2: Recall that different versions of the same gene at a particular locus are known as alleles. Step 3: Compare the term alleles with other genetics terms: genomes refer to the entire genetic material, genotypes refer to allele combinations, and gene pools refer to all genes in a population. Step 4: Conclude that the only correct term for different forms of the same gene is alleles.

Verification / Alternative check:
Think of the ABO blood group system. The ABO gene has multiple alleles, such as IA, IB, and i. These are different forms of the same gene and clearly demonstrate that the correct term for such variants is alleles. Textbooks consistently define alleles as alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

Why Other Options Are Wrong:

• Option A (Genomes): A genome is the complete set of DNA in an organism, not a form of a single gene.
• Option C (Genotypes): A genotype is the combination of alleles an individual has, not the individual forms themselves.
• Option D (Gene pools): A gene pool is the collection of genes in a population, not different versions of a single gene.

Common Pitfalls:
Learners sometimes mix up allele and genotype. Remember that an allele is a single version of a gene, while genotype describes the pair or set of alleles that an organism carries. Another pitfall is thinking that genome or gene pool refers to small units like alleles, but those terms describe much larger collections of genetic information.

Final Answer:
Different forms of the same gene are called alleles.