The terms, dominant and recessive describe the inheritance patterns of certain traits. The terms are useful concepts when it comes to predicting the probability of an individual inheriting certain phenotypes, especially genetic disorders. However, the terms can be confusing when it comes to understanding how a gene specifies a trait.
In genetics, dominance can be described as the phenomenon of one variant of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. In other words, an individual receive two versions of each gene, referred to as alleles, from each parent. If the alleles of a gene are different, one allele will be expressed; it is the dominant gene. The effect of the other allele, referred to as recessive is masked.
What Is A Dominant Gene/Factor/Trait/Allele?
A dominant gene or a dominant version of a gene, is a particular variant of a gene which for a variety of factors, expresses itself more strongly all by itself than the other version of the gene which the person is carrying. The other version of the gene is recessive. They are masked by the dominant phenotype and you need to get two copies of that trait to see it in your phenotype.
Dominant alleles show their effect even if the individual only has one copy of the allele also referred to as being heterozygous. For example, the allele for brown eyes is dominant, therefore you only need one copy of the brown-eye allele to have brown eyes (although, with two copies you will still have brown eyes).
However, in cases where both alleles are dominant, it is referred to as codominance. The resulting characteristic is due to both alleles being expressed equally. An example of this is the blood group AB which is the result of codominance of the A and B dominant alleles.
Most dominant traits are due to genes located on the autosomal (the no-sex chromosomes).an autosomal dominant trait typically affects males and females with equal likelihood and with similar severity. Examples of dominant disorders include:
- Polycystic kidney disease
- Achondroplasia (a common form of dwarfism with short arms and legs).
- Familial hypercholesterolemia (high blood cholesterol leading to premature coronary artery disease).
- Hunington disease (a form of progressive dementia)
- Neurofibromatosis (a neurologic disorder with an increased risk of malignant tumors).
What You Need To Know About Dominant Genes
- A dominant allele is a gene that produces its effect (expresses itself) in the presence of the other (recessive) allele.
- Recessive genes always express the dominant trait.
- It does not require another similar allele to produce its effect on the phenotype e.g Tt is tall.
- Dominant allele or trait can form complete polypeptide or enzyme for expressing its effects e.g red color of flower in Pea.
- The dominant genes mask the effect of the recessive genes.
- Example of dominant trait is Brown eyes, A and B blood type.
- It is written in Uppercase Letter (T).
- Dominant gene is more likely to be inherited.
- The dominant gene is more prone to produce diseases.
What Is A Recessive Gene/Factor/Trait/Allele?
A recessive gene is a gene whose effects are masked in the presence of a dominant gene. They are only expresses when they encounter other recessive genes. That is, for the characteristics that are related to the recessive alleles to be made visible, it is necessary that both parents have the required recessive alleles.
A recessive gene is only expressed when an organism has two recessive alleles for that gene. This is also referred to as being homozygous recessive. If an organism has one dominant and one recessive allele, it will show the dominant trait. For example, natural hair color might be brown, black, blonde or red. For each trait, you get alleles from each parent, how these are expressed largely depends upon which one dominates the other. Example of recessive trait is Blue eyes and O blood type.
What You Need To Know About Recessive Genes
- A recessive allele is a gene whose effect is not expressed unless it is present as a homozygous form in the organism. Both alleles must be identical for the gene to express itself in the organism.
- Recessive genes express the recessive trait.
- It produces its phenotypic effect only in the presence of a similar allele e.g tt is dwarf.
- The recessive allele forms an incomplete or defective polypeptide or enzyme so that the expression consists of absence of the effect of dominant allele e.g white flower color in Pea.
- Recessive genes are unable to mask the effect of the dominant genes.
- Example of recessive trait is Blue eyes and O blood type.
- It is written in Lowercase letter (t).
- Recessive gene is less likely to be inherited.
- Recessive gene is less prone to produce diseases.
Difference Between Dominant And Recessive Genes In Tabular Form
|BASIS OF COMPARISON||DOMINANT GENES||RECESSIVE GENES|
|Description||A dominant allele is a gene that produces its effect (expresses itself) in the presence of the other (recessive) allele.||A recessive allele is a gene whose effect is not expressed unless it is present as a homozygous form in the organism.|
|Expression||Recessive genes always express the dominant trait.||Recessive genes express the recessive trait.|
|Effect||It does not require another similar allele to produce its effect on the phenotype e.g Tt is tall.||It produces its phenotypic effect only in the presence of a similar allele e.g tt is dwarf.|
|Polypeptide Or Enzyme||Dominant allele or trait can form complete polypeptide or enzyme for expressing its effects e.g red color of flower in Pea.||The recessive allele forms an incomplete or defective polypeptide or enzyme so that the expression consists of absence of the effect of dominant allele e.g white flower color in Pea.|
|Effect Masking||The dominant genes mask the effect of the recessive genes.||Recessive genes are unable to mask the effect of the dominant genes.|
|Examples||Example of dominant trait is Brown eyes, A and B blood type.||Example of recessive trait is Blue eyes and O blood type.|
|How It Is Written||It is written in Uppercase Letter (T).||It is written in Lowercase letter (t).|
|Inheritance||Dominant gene is more likely to be inherited.||Recessive gene is less likely to be inherited.|
|Susceptibility To Diseases||The dominant gene is more prone to produce diseases.||Recessive gene is less prone to produce diseases.|
Also Read: Difference Between Genotype And Phenotype