Here's a breakdown:
* Alleles: Different versions of the same gene. For example, the gene for eye color can have alleles for blue eyes, brown eyes, or green eyes.
* Gene Locus: The specific location of a gene on a chromosome.
* Dominant Allele: An allele that will be expressed even if only one copy is present in the organism (heterozygous genotype).
* Recessive Allele: An allele that will only be expressed if two copies are present in the organism (homozygous genotype).
Example:
Let's say the gene for eye color has two alleles: brown (B) and blue (b).
* BB: Homozygous dominant - individual will have brown eyes.
* Bb: Heterozygous - individual will have brown eyes (brown allele is dominant, masking the blue allele).
* bb: Homozygous recessive - individual will have blue eyes (no dominant allele to mask the blue allele).
Why dominance happens:
The dominant allele typically produces a functional protein that results in a specific trait. The recessive allele might produce a non-functional protein or no protein at all. The presence of the functional protein from the dominant allele overrides the lack of a functional protein from the recessive allele.
Important Note:
Dominance is not always complete. There are cases of:
* Incomplete dominance: The phenotype of the heterozygote is a blend of the two homozygous phenotypes.
* Codominance: Both alleles are expressed equally in the heterozygote.
While the concept of dominance can seem simple, the underlying mechanisms are complex and involve intricate molecular interactions.
