Question

What are Alleles?

• A. two genes that occupy the different position on non-homologous chromosomes and that cover the same trait
• B. two genes that occupy the same position on homologous chromosomes and that cover the same trait
• C. two genes that occupy the same position on non-homologous chromosomes and that cover different trait
• D. two genes that occupy the same position on homologous chromosomes and that cover different trait

Hint:

• Gene A segment of DNA that codes for a functional product (e.g., a protein).
• Locus The specific physical location of a gene on a chromosome.
• Homologous Chromosomes Pairs of chromosomes (one from each parent) that have the same genes in the same order, but may have different alleles for those genes.
• Alleles Different versions of the same gene found at the same locus on homologous chromosomes. They code for the same trait (e.g., eye color) but can produce different phenotypes (e.g., blue eyes, brown eyes).

Answer 1

The Correct Option is B

Alleles are alternative forms of a gene that arise by mutation and are found at the same place (locus) on homologous chromosomes. They control the same trait but may result in different expressions of that trait. Let's analyze the options:
(a) "...different position on non-homologous chromosomes...": Incorrect. Alleles are at the same locus on homologous chromosomes.
(b) "...same position (locus) on homologous chromosomes and that cover the same trait": Correct. This accurately describes alleles. For example, the gene for flower color in peas might have an allele for purple flowers and an allele for white flowers, both located at the flower color locus on homologous chromosomes.
(c) "...same position on non-homologous chromosomes...different trait": Incorrect on both counts regarding chromosome type and trait.
(d) "...same position on homologous chromosomes...different trait": Incorrect. Alleles for a specific gene control the same trait (e.g., flower color), though they may lead to different phenotypes (e.g., purple vs. white).
Therefore, option (b) is the correct definition of alleles. \[ \boxed{\text{two genes that occupy the same position on homologous chromosomes and that cover the same trait}} \]