Difference Between Homozygous and Heterozygous (With Table)

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.

Homozygous vs Heterozygous 

The difference between homozygous and heterozygous is that both of them have a different number of forms they can occur in. Homozygous can occur in two different forms, whereas heterozygous can only occur in one form. They have different potential genotypes; in the case of homozygous, it can only be either AA (dominant) or aa (recessive), while in the case of heterozygous, it can also be Aa (dominant and recessive). Mendel gave different terms to both of them. He gave true-breeding for homozygous and hybrid for heterozygous along with this, he also explained that homozygous as being present on both chromosomes is always expressed phenotypically while as heterozygous being recessive will be carried away and not expressed phenotypically and being dominant will always be expressed phenotypically. They also differ in other terms that are mentioned below.

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 gene representing eye color contains 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, and one of them is dominant, and another one is recessive for example, one gene representing eye color contains the brown and is dominant, whereas the other one contains black and recessive then these can be termed as Heterozygous genes. 

Comparison Table Between Homozygous and Heterozygous 

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 gene representing eye color contains 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 for self-breeding, which leads to the production of traits that can be further passed down to the next generations.

Same traits over the generation happen in Homozygous during self breeding. Homozygous do not show any extra vigor. There are two types of the homozygous present in the world, which are homozygous-dominant and homozygous-recessive. Homozygous-dominant is a case where both the genes are dominant in nature, whereas homozygous-recessive is the trait where both genes show recessive behavior in the application of genes. In homozygous diseases that occur can be sickle-cell anemia 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, and one of them is dominant, and another one is recessive for example, one gene representing eye color contains the 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 a 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 heterozygous, incomplete heterozygous, and codominance. 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. 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 different two types of 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 anemia and steroid-resistant nephrotic syndrome, whereas disease that can occur in heterozygous can be Huntington’s disease.

Conclusion 

Therefore, with all the above differences, it will be clear how both homozygous and heterozygous are different. They are similar in some terms as well. This includes they both show vigor, they are two copies of the same alleles making up a particular gene, they are responsible for showing traits, etc. They are important to understand because they are the reason why you look the way you are or act the way you do it all because of your genes and can be due to both of your parents like in homozygous or because of a single one like in case of heterozygous.

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
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