Here's a breakdown:

* Gene: A segment of DNA that codes for a specific protein or functional RNA molecule.

* Allele: A variant form of a gene. For example, the gene for eye color might have alleles for blue eyes, brown eyes, and green eyes.

* Genotype: The specific combination of alleles an individual possesses for a particular gene.

* Phenotype: The observable characteristics or traits of an individual, determined by their genotype.

Let me know if you have any other questions!