Alleles are best described as b) alternative forms of a gene for a single trait such as blue eyes and brown eyes. Each gene can have multiple variations, known as alleles, which determine specific traits within an organism.
For example, the gene responsible for eye color might have one allele for blue eyes and another for brown eyes. Individuals inherit two alleles for each gene, one from each parent, and it is the combination of these alleles that influences the trait expressed.
The other options provided do not accurately describe alleles:
- a) refers to the concept of dominance and recessiveness, which is related but not a definition of alleles themselves.
- c) talks about the locations of genes on chromosomes, which is about the physical position of genes rather than their variations.
- d) appears incomplete and does not pertain to the specific definition of alleles.
In summary, alleles are crucial in genetics as they contribute to the diversity of traits among individuals.