A gene is a piece of DNA or RNA that controls a trait, such as skin or eye color. allele is the specific variation of the gene, which will determine how this characteristic will be expressed in the individual. For example, the eye color gene has many alleles, such as alleles for blue, brown, or green eye color.
The genes that we inherit are the same for all human beings, while the alleles are inherited from the mother and the father, always occurring in pairs. These alleles can be the same (homozygous) or different (heterozygous), and in the case of heterozygotes, the dominant allele is what will be expressed as a trait.
| Gene | allele | |
|---|---|---|
| Definition | A section of DNA that controls a certain trait. | A specific variation of a gene, which determines how the trait will be expressed in an individual. |
| occurrence in pairs | No. | Yes. |
| Example | Eye color, blood type, skin color. | Blue eyes, green eyes, type A blood, black skin, white skin. |
Definition of Gene
Genes are the different parts of DNA that decide what genetic traits a person will have. They provide the direction to produce a specific protein, responsible for the traits.
Genes are on chromosomes, which are strands of DNA wrapped around proteins. The genes that people have are the same, but they can exist in different types, which we call alleles.
Definition of Allele
Alleles are the different types of the same gene, which determine a single trait in an individual. They are the physical expression of the genes themselves.
For example, if your eye color was decided by a single gene, one of the alleles could carry the blue color, which came from its mother, while the other allele could carry the brown color, which came from its father. Then, the dominant allele would be expressed and define what your eye color would be.
Gene and allele function
The gene is the basic unit of heredity, as it defines the characteristics that each individual will have.
This is because a gene is a stretch of DNA that encodes a polypeptide through an RNA chain. It is these coded chains that give the characteristics of each individual, such as eye color and blood type.
An allele is a variation of a gene. They lead to the encoding of different RNA strands and therefore different characteristics.
Homozygous and Heterozygous
Each organism has two alleles for each gene, one on each chromosome. If the two alleles are identical, they are called homozygous. In this case, the two alleles will indicate the same trait, such as blue eyes.
But if they are different, for example, one indicating blue eyes and the other indicating brown eyes, they are called heterozygotes. In the case of heterozygotes, the individual may manifest one of these characteristics or a combination of the two.
See also the difference between:
- genotype and phenotype
- dominant and recessive
- Homozygous and heterozygous
