Key Features:
- Gene Variants: Alleles are different versions of the same gene, each with a slightly different DNA sequence.
- Locus Specificity: Alleles occupy the same specific location on a chromosome, known as the locus.
- Pairwise Occurrence: In diploid organisms (like humans), individuals inherit two alleles for each gene, one from each parent.
- Phenotypic Variation: Alleles contribute to the variation in traits observed in individuals.
Example:
Consider the gene for eye color. There may be multiple alleles for this gene, such as:
- Brown allele (B): Produces brown eyes
- Blue allele (b): Produces blue eyes
An individual may inherit two brown alleles (BB), one brown and one blue allele (Bb), or two blue alleles (bb). These combinations will determine their eye color.
Significance:
Alleles are crucial for:
- Genetic diversity: They create variation within populations, providing the raw material for evolution.
- Inheritance: Alleles are passed down from parents to offspring, determining their traits.
- Disease susceptibility: Some alleles may be associated with an increased risk of certain diseases.
Summary:
Alleles are alternative versions of a gene that contribute to genetic diversity, inheritance, and phenotypic variation. They play a fundamental role in shaping the characteristics of individuals and populations.
