Homozygous vs Heterozygous: Difference and Comparison

Every human has DNA that has different genes. Many of these genes are common for all humans, whereas some are varied in every human.

These variations are the responsible ones to make every human unique.

These variations are known alleles in biological terms, and every human contains two alleles for the same gene, one contributed by the parent mother and another one from the biological father.

They can be of two types only, i.e., Homozygous and Heterozygous.

Key Takeaways

  1. Homozygous refers to having two identical alleles for a gene, while heterozygous refers to having two different alleles.
  2. Homozygous individuals exhibit pure breeding, while heterozygous individuals exhibit hybrid breeding.
  3. Homozygous individuals are more susceptible to inherited diseases if the gene carries a disease-causing mutation.

Homozygous vs Heterozygous 

Homozygous means to have identical alleles of a particular gene or to have inherited the same versions of a genomic market from biological parents. Heterozygous is used to define having two different alleles of particular genes, and they have a particular trait. It is used to describe a cell, nucleus or organism.

Homozygous vs Heterozygous

The genes which contain the variations that are why every human is different.

When the gene passed to the child by the biological parents contains the same variant, for example, both genes representing eye color containing the same color can be termed as homozygous genes.  

Some genes contain variations that make every human different.

When the gene passed to the child by the biological parents contains two variants, one of them is dominant, and another one is recessive; for example, one gene representing eye color contains brown and is dominant, whereas the other one contains black and recessive then these can be termed as Heterozygous genes. 

Comparison Table

Parameters of ComparisonHomozygousHeterozygous 
Number of forms TwoOne
Potential genotypesAA or aaAa
Mendel’s termTrue-breedingHybrid
DiseasesSickle-cell amenia, nephrotic syndrome Huntington’s disease.
Mendelian genetics Always expressedIt cannot be expressed unless dominant

What is Homozygous?

The genes which contain the variations that are why every human is different.

When the gene passed to the child by the biological parents contains the same variant, for example, both genes representing eye color containing the same color can be termed as homozygous genes.

Homozygous is the code of a particular trait due to the presence of copies of two alleles of the same type passed by the biological mother and father.

It is also responsible for gametes. Homozygous is also responsible for the production of a single or only one type of gamete.

Another responsibility it faces is self-breeding, which leads to the production of traits that can be further passed down to the next generations.

The same traits over the generations happen in Homozygous during self-breeding. Homozygous do not show any extra vigour.

There are two types of homozygous present in the world, which are homozygous-dominant and homozygous-recessive.

Homozygous-dominant is a case where both genes are dominant in nature, whereas homozygous-recessive is the trait where both genes show recessive behaviour in the application of genes.

In homozygous diseases that occur can be sickle-cell anaemia and steroid-resistant nephrotic syndrome.

What is Heterozygous?

Some genes contain variations that make every human different.

When the gene passed to the child by the biological parents contains two variants, one of them is dominant, and another one is recessive; for example, one gene representing eye color contains brown and is dominant, whereas another one contains black and recessive then these can be termed as Heterozygous genes.

Heterozygous is of a particular gene and has a set of two different copies of alleles. Heterozygous have both of them (dominant or recessive), for example, Tt.

The dominant one rules and show its variation in the human, but the human play the role of the carrier in this and other generation can have an impact due to this recessive gene.

Heterozygous have both types of gametes (both with the help of dominant and recessive alleles). The combination of several traits over the generation takes place in heterozygous during self-breeding.

With heterozygous, it can show some extra vigor, which is known as hybrid vigor. There are three types of heterozygous: complete, incomplete, and codominant.

Diseases that can occur in heterozygous can be Huntington’s disease.

Main Differences Between Homozygous and Heterozygous 

  1. Homozygous is the code of a particular trait due to the presence of copies of two alleles of the same type, whereas heterozygous is of a particular gene and set of two different copies of alleles.
  2. Both of them can have dominant or recessive alleles. In the case of homozygous, it can be either of them (dominant or recessive). An example of this can be TT or tt, whereas heterozygous can have both of them (dominant or recessive), for example, Tt.
  3. Both of them are responsible for gametes. The difference is in the types of gametes they produce. Homozygous is responsible for the production of a single or one type of gamete, whereas heterozygous types of gametes (both with the help of dominant and recessive alleles).
  4. They are responsible for self-breeding, which leads to the production of traits. The same traits over the generation happen in Homozygous during self-breeding, whereas the combination of several traits over the generation takes place in heterozygous during self-breeding.
  5. Both of them show little or more vigor. In the case of homozygous, it does not show any extra vigor, whereas with heterozygous, it can show some extra vigor which is known as hybrid vigor.
  6. There are two different types: homozygous and heterozygous. Two types of homozygous are homozygous-dominant and homozygous-recessive, and types of heterozygous are complete heterozygous, incomplete heterozygous, and codominance.
  7. The disease can occur in both of them; in homozygous, diseases that occur can be sickle-cell anaemia and steroid-resistant nephrotic syndrome, whereas disease that can occur in heterozygous can be Huntington’s disease.
References
  1. https://academic.oup.com/jcem/article-abstract/74/3/685/2653099
  2. https://www.sciencedirect.com/science/article/pii/014067369192449C
  3. https://www.nature.com/articles/nature17664

Last Updated : 04 September, 2023

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22 thoughts on “Homozygous vs Heterozygous: Difference and Comparison”

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