Genetics plays a major role in determining our physical and behavioral traits. There are two major types of alleles in inheritance, dominant and recessive. Understanding the difference between these two alleles can give us a better understanding of how traits are passed down from one generation to the next.
Dominant Gene/Factor/Trait/Allele
1. Expressiveness
A dominant allele is able to express itself even in the presence of its recessive allele. This means that the phenotype (physical or behavioral trait) produced by the dominant allele will be visible, even if an individual has one dominant and one recessive allele.
Example: In pea plants, the gene for tallness is dominant, meaning that if an individual has one dominant allele for tallness (T) and one recessive allele for shortness (t), the plant will still grow tall. This is because the dominant allele (T) will express its phenotype (tallness) in the presence of the recessive allele (t).
2. Similar Allele Requirement
A dominant allele does not require another similar allele to produce its effect on the phenotype. This means that an individual can have just one dominant allele to express the phenotype produced by that allele.
Example: In pea plants, if an individual has one dominant allele for tallness (T) and one recessive allele for shortness (t), the plant will still grow tall. This is because the dominant allele (T) does not require another similar allele to produce its effect on the phenotype.
3. Polypeptide or Enzyme Formation
A dominant allele or factor can form a complete polypeptide or enzyme for expressing its effects. This means that the dominant allele is capable of producing the necessary protein or enzyme for expressing its phenotype.
Example: In pea plants, the dominant allele for red flower color can form a complete polypeptide or enzyme for expressing the red flower color. This is why a plant with one dominant allele for red flower color and one recessive allele for white flower color will still have red flowers.
Recessive Gene/Factor/Trait/Allele
1. Expressiveness
A recessive allele is unable to express itself in the presence of a dominant allele. This means that the phenotype produced by the recessive allele will not be visible if an individual has one dominant and one recessive allele.
Example: In pea plants, the gene for shortness is recessive, meaning that if an individual has one dominant allele for tallness (T) and one recessive allele for shortness (t), the plant will still grow tall. This is because the dominant allele (T) will express its phenotype (tallness) in the presence of the recessive allele (t), preventing the recessive allele from expressing its phenotype (shortness).
2. Similar Allele Requirement:
A recessive allele produces its phenotypic effect only in the presence of a similar allele. This means that an individual must have two recessive alleles to express the phenotype produced by that allele.
Example: In pea plants, an individual must have two recessive alleles for shortness (tt) to express the phenotype of shortness. This is because the recessive allele will only produce its phenotypic effect in the presence of another similar allele.
3. Polypeptide or Enzyme Formation
The recessive allele forms an incomplete or defective polypeptide or enzyme, so the expression consists of the absence of the effect of the dominant allele. This means that the recessive allele will not produce the desired phenotype unless it is paired with another recessive allele. This is why a recessive trait or characteristic may only show up in individuals who have received two copies of the recessive allele, one from each parent.
For example, consider the gene that controls flower color in peas. The dominant allele (T) codes for the production of pigments that produce a red flower color, while the recessive allele (t) codes for the absence of these pigments, resulting in a white flower color. If an individual has a dominant allele from one parent and a recessive allele from the other, it will have a red flower color (TT or Tt). However, if the individual has two copies of the recessive allele (tt), it will have a white flower color.
In another example, consider the gene that determines the height of a plant. The dominant allele (T) produces a tall plant, while the recessive allele (t) produces a short plant. If an individual plant has one dominant allele and one recessive allele (Tt), it will be tall. However, if it has two copies of the recessive allele (tt), it will be short.
Dominant vs Recessive Genes: Differences
| Feature | Dominant Gene | Recessive Gene |
|---|---|---|
| Ability to Express | Can express itself even in the presence of its recessive allele | Unable to express itself in the presence of dominant allele |
| Similar Allele Required | No | Yes |
| Phenotypic Effect | Produces its effect even with one dominant allele | Produces its effect only in the presence of a similar allele |
| Polypeptide or Enzyme Formed | Forms complete polypeptide or enzyme | Forms an incomplete or defective polypeptide or enzyme |
Note: Example of phenotypic effect given in the article is “tall” for dominant allele and “dwarf” for recessive allele in pea plant height. Example of polypeptide or enzyme formation given in the article is “red color of flower” for dominant allele and “white flower color” for recessive allele in pea plant flower color.
