Homozygous vs Heterozygous: Definition and Differences
Homozygous vs Heterozygous
Features of Homozygous
Homozygous refers to the state of the genes or genetic condition in which an individual has inherited the similar DNA sequence for a particular gene from both their biological parents and it is generally used with reference to the disease.
For instance, if an individual inherited a mutated allele in the DNA sequence from maternal side and similar gene from the paternal part as well, then the mutation is explained as homozygous for that individual.
Thus, after receiving 2 identical copies of the gene, detrimental effects will express phenotypically for which the genes are coded.
The term “heterozygous” attribute to a pair of alleles so heterozygous is when you have 2 dissimilar alleles that means you have received dissimilar copies from each parent.
In a heterozygous genotype, the allele which is dominant dominates over recessive and hence the dominant feature will be expressed while the recessive will not show but you will be still a carrier.
This will be passed it on to your children. Homozygous is the opposite of the heterozygous where the feature of the similar alleles — either dominant or recessive — is manifested.
There are three possible alleles for A, B, O blood type. However, the contribution from each parent’s gene makes a difference an individual exhibit with phenotypic characteristic.
Sometimes, it may be possible that both the parents pass on the same allele for a gene, making it a homozygous trait.
While in certain conditions, different set of alleles are triggered resulting in heterozygous trait.
A homozygous trait is mainly responsible for phenotypic appearance in the organism. A pea plant will definitely exhibit long stem, if it receives two alleles associated with tallness. In contrast, if it gets two “short” alleles, then plant with stunted growth will be evident.
Thus, for a specific characteristic, the genotype may be either homozygous or heterozygous, however, the way it is expressed it is identified as phenotype.
Features of Heterozygous
Heterozygous is a genetic condition where an individual inherits different alleles of a gene from the two parents.
Heterozygosity is observed in a diploid organism where a gene contains two different alleles at a gene locus.
In heterozygous chromosomes, the two alleles are different, and the heterozygous genotypes are represented by a capital letter, which indicates the dominant allele and a lowercase letter, which indicates the recessive allele, like Bb for eye color.
In heterozygous chromosomes with genes having traits that are expressed via complete dominance, only the trait coded by the dominant allele is expressed.
In complex dominance schemes, however, the expression of genes is more complicated. In incomplete dominance, the phenotypic trait observed is somewhere between dominant and recessive phenotypes.
Similarly, in co-dominance, the phenotypes are expressed by individual alleles in different parts of the body.
The heterozygous genotype has relatively higher fitness than the homozygous-dominant or homozygous-recessive genotypes. This fitness is termed as ‘hybrid vigour’.
Organisms reproducing by sexual breeding mechanisms are usually heterozygous for the traits that are varied.
Methods of sexual reproduction result in heterozygous chromosome formation. This ensures that the phenotypic characteristic in the offsprings is different from that in the parents.
Mostly, heterozygosity is defined at the specific locus where copies of the gene affecting a trait present on the two reciprocal homologous chromosomes are different.
Heterozygous cells or organisms are also called heterozygotes. As with homozygous genotypes, some heterozygous genotypes are also often associated with genetic conditions.
If the mutated allele is dominant, only the mutated copy is capable of causing the disease. This condition is called dominant-disease.
If the mutated allele is recessive, then the disease will not appear, and the organism will act as a carrier.
Diseases like Huntington’s disease, Marfan’s syndrome, and familial hypercholesterolemia are associated with heterozygous genotypes.
Homozygous vs Heterozygous
| Comparison | Homozygous | Heterozygous |
| Definition | Homozygous is a hereditary condition where an individual acquires similar alleles of a quality from both the parents. | Heterozygous is a hereditary condition where an individual acquires various alleles of a quality from the two guardians. |
| Genotype representation | Homozygous genotypes are addressed as AA or aa for homozygous-prevailing or homozygous-latent conditions, respectively. | Heterozygous genotypes are addressed by Aa genotypes. |
| Phenotypes | Two various aggregates are conceivable with prevailing or latent homozygous conditions. | The aggregate is for the most part because of the predominant allele in the heterozygous condition. |
| Gametes | Homozygous genotypes bring about a solitary sort of gamete. | Heterozygous genotypes bring about two distinct kinds of gametes. |
| Traits | Homozygous genotypes produce similar qualities over various generations. | Heterozygous genotypes produce various characteristics over various ages. |
| Half and half vigour | The homozygous condition doesn’t show mixture vigour. | Heterozygous condition shows cross breed energy. |
| Types | Homozygous-prevailing and homozygous-passive are two kinds of homozygous conditions. | The heterozygous condition can be communicated in three unique manners; co-strength, deficient predominance, and complete predominance. |
| Additionally called | Organisms or cells with the homozygous condition are named as homozygotes. | Organisms or cells with the heterozygous condition are named as heterozygotes. |
| Noticed in | Homozygous genotypes are seen in creatures repeating by agamic means. | Heterozygous genotypes are generally found in creatures duplicating by sexual means. |
| Diseases | Common illnesses related with the homozygous condition incorporate fibrosis, sickle cell frailty, and phenylketonuria. | Common sicknesses related with the heterozygous condition incorporate Huntington’s infection, Marfan’s disorder, and familial hypercholesterolemia. |
Examples of Homozygous vs Heterozygous
Instances of heterozygous genotypes: Sickle-cell anaemia: The attribute for sickle-cell disorder is a passive characteristic that makes the platelets be shaped inaccurately.
Accordingly, in people with heterozygous genotype, the prevailing characteristic is communicated, forestalling the sickle-cell pale condition.
In sickle-cell paleness, the red platelets change its design into sickle-morphologic characteristics, which makes it little and lacking to convey sufficient oxygen.
Along these lines, the heterozygous genotype of the quality liable for sickle-cell iron deficiency gives a benefit to such people.
Wavy hair: The predominant attribute for hair type is wavy; subsequently, just individuals with homozygous-passive alleles have straight hair.
This quality codes for the protein that makes the hair be wavy. Heterozygous genotype makes the hair in such people be wavy, which is among wavy and straight hair.
This marvel is additionally called fragmented predominance, where the aggregate communicated is between the prevailing and passive ones.
In complete strength, the wavy hair straight is seen in people with the heterozygous condition.
Homozygous vs Heterozygous Citations
- Do heterozygous HTRA1 mutations carriers form a distinct clinical entity?CNS Neurosci Ther . 2018 Dec;24(12):1299-1300.
- Selective effects of heterozygous protein-truncating variants. Nat Genet . 2019 Jan;51(1):2.
- Managing Patients With Homozygous Familial Hypercholesterolemia. J Am Coll Cardiol . 2017 Aug 29;70(9):1171-1172.
- Multisystem presentation of a homozygous POLG2 variant. Eur J Med Genet . 2020 May;63(5):103899.
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