Difference Between a Gene and an Allele

Edited by Diffzy | Updated on: August 18, 2023

       

Difference Between a Gene and an Allele

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Introduction

Fundamental genetics depends on both genes and alleles. Alleles are distinct versions of a gene that differ depending on the nucleotide base present at a certain genomic site, whereas genes are segments of DNA that code for proteins that affect physiology. Each gene in humans has two copies, one from each parent, and alleles play a crucial part in determining the distinctive qualities of each individual. Although alleles can be identical, they frequently contain little variances. In diploid organisms, each attribute is made up of two components known as alleles: the dominant allele and the recessive allele. A gene defines a certain trait, but an allele introduces variants to a single trait. This is the main distinction between a gene and an allele.

Gene vs Allele

The genetic makeup of life is determined by both genes and alleles. Within the structure of chromosomes lie genetic sequences acknowledged as genes. These genes hold the blueprint for an individual's growth, operations, and reproductive processes essentially, the diverse characteristics exhibited by the individual. Every characteristic is governed by a pair of elements termed alleles in organisms with two sets of chromosomes (diploid). One of these elements is observable and referred to as the dominant allele, while the other remains concealed, known as the recessive allele.The key difference between a gene and an allele is that a gene is a stretch of DNA that determines a specific trait and an allele brings variations to a single trait.                 

Difference Between Gene and Allele in Tabular Form

ComparisonGeneAllele
DefinitionA gene is a section of DNA that regulates a certain trait.An allele is a particular gene's variety. It displays many phenotypic variations for the same characteristic.
NumbersA single gene determines a particular trait.Variations in the characteristic are brought about by two or more alleles.
LocationGenes are found in all known organisms.Alleles can be identified in multi-­genome organisms.
OccurrenceGenes occur as single units.Alleles always occur in pairs.
Genetic makeupCreate the individual.Bring differences to individuals in a population.
InfluenceGenes encode for a single protein.Allele produces  the opposite phenotype.

What is a Gene?

A gene is a chromosomal area (locus) or a sequence. It contains the amino acid composition of a particular protein. In higher creatures, a single chromosome has thousands of genes. The gene is accepted as the hereditary molecular unit. Through genetic reproduction, the genetic instructions are passed onto progeny. Proteins are produced by translating RNA from gene sequences. This is referred to as the fundamental principle of molecular biology.

In prokaryotes, the genes assemble into operon-containing structures. Functionally similar genes are transcribed collectively in options. Untranslated regions, introns, and exons make up eukaryotic genes. Genes in prokaryotes are intronless. Introns aid in the transcription of genes. As a result, they are eliminated through exon splicing. Alternative splicing can result in the production of many proteins. At both the transcriptional and translational levels, gene expression is controlled.

Types of Genes

Complementary Genes

To manifest the targeted phenotype, a collaborative interplay of paired dominant genes is required. The desired observable trait materializes exclusively when both genetic components are concurrently present. Neither a standalone dominant gene nor an isolated recessive gene can adequately express the trait autonomously. The two dominant genes synergistically engage to achieve the intended outcome.

Supplementary Genes

Distinct from supplementary genes, the interdependent nature of complementary genes facilitates the emergence of a specific phenotype. Among supplementary genes, a singular dominant gene possesses the capability to independently exhibit its characteristics, with a secondary gene also holding self-expressive potential. However, the latter gene requires pairing with the former to activate its expression. This coupling of the two genes engenders the possibility of giving rise to an entirely distinct attribute or phenotype.

The union of two mice, one black and one albino, is a typical illustration used to explain this gene type. Albino mice cannot grow a colored coat on their own, but when they are crossed with black mice, the resulting offspring expresses a coat color that is neither black nor white but a new brown color.

Duplicate Genes

Duplicate genes live up to their name. It happens when two genes express themselves in the same way, whether they are recessive or dominant. Each individual has freely decided how they want to express themselves and will do so regardless of the other, therefore one does not need the other to exhibit a particular phenotype. The idea that these genes can reproduce the phenotype's characteristics is intriguing.

Polymeric Genes

Due to the fact that they have an additive or compounding influence on one another, polymeric genes, often referred to as additive genes, are comparable to duplicate genes. There isn't always a pair of polymeric genes that express themselves in the same way, though.

Sex-Linked Genes

These genes affect the X or Y chromosomes, which control sex and how certain features are inherited dependent on sex. Even recessive features on X chromosomes from XX persons (females) are more likely to be represented in XY individuals since those with XY chromosomes (males) have only one X chromosome.

What is Allele?

Genetic diversities known as "alleles" encompass alternative manifestations of a specific gene. These variances give rise to distinct phenotypic characteristics. Although genetic sequences might exhibit dissimilarities, a considerable portion of gene mutations elude noticeable changes, evading overt alterations. Diploid organisms accommodate homologous chromosomes, where a particular gene can occupy corresponding positions on either member of a chromosomal pair. In instances where the sequences of these chromosomal sites exhibit perfect congruence, the alleles are denoted as homozygous at that locus. Conversely, if disparate sequences manifest at these sites, the alleles are identified as heterozygous at that locus. Within scenarios of allelic heterozygosity, a sole phenotypic attribute frequently exerts dominance, relegating the other to a recessive stature.

The dominant allele, also known as the wild type, is widespread in nature. Recessive alleles are rather uncommon and are referred to as mutants. Sometimes no allele in the pair is dominant, resulting in the expression of both alleles. This state is classified as co­dominant; co­dominant allele expression can be seen in the inheritance of the human AB blood type. When one allele in a pair is only partially dominant over the other allele, this is known as incomplete dominance. The color inheritance of the pink flower in tulips is an illustration of incomplete dominance. The genotypic interactions between the two alleles are described by the terms dominant and recessive alleles.

Types of Alleles

Alleles are unique gene variants that may exist at any particular genomic locus or loci. The child receives two copies of each parent's human genome. Dominant, recessive, codominant, and incomplete dominant alleles are the four different types of alleles.

Dominant Alleles

A dominant allele is a gene variant that causes a certain trait even when there are multiple alleles present. It is a variant of a gene that produces enough enzymes to provide a cell with an abundance of a certain product while also encoding a functional protein. A combination of a dominant and a recessive allele for a gene will yield an individual displaying the dominant phenotype. In the realm of genetics, the concept of "dominance" delineates the mechanism whereby a specific version of a gene on one chromosome suppresses or prevails over the influence of an alternate version of the same gene on the companion chromosome.

Genetic characteristics referred to as dominant alleles govern observable attributes such as freckles, chin dimples, hair texture (curliness or straightness), hair color (dark or light), baldness, and immunity to poison ivy. A heterozygous set of alleles causes an individual to manifest the dominant trait. For instance, the dominant allele for brown eyes. Huntington's disease is caused by a dominant mutation, meaning that regardless of the person's other Huntington disease gene allele, if they carry that particular form of the Huntington gene, they will develop the condition. In peas, where peas may be round (related to allele R) or wrinkled (associated with allele R), complete dominance is the transmission of seed form.

Recessive Allele

In the presence of a dominant allele, a recessive allele, or a specific type of genetic coding, fails to manifest a discernible phenotype. The prevailing influence of the dominant allele in a relationship between dominant and recessive alleles tends to overshadow the effects of the recessive counterpart. Only individuals who carry a homozygous configuration, possessing two identical alleles, can exhibit the manifestations associated with recessive alleles.                                                                        For instance, a dual presence of the 'blue eye' allele is requisite for the expression of blue eye color. Hereditary abnormalities in the CFTR gene are the cause of the hereditary disease cystic fibrosis (CF), which affects the digestive and respiratory systems. People who have two recessive alleles (homozygous recessive) get this condition.

The allele for slender brows is recessive. You may tell someone has recessive alleles by looking at them because they have a cleft in their chin. The same holds for short eyelashes, an even skin tone, connected eyebrows, and a straight hairline.

Co-dominant Allele

A prevailing allele signifies a genetic version that bestows a specific trait's expression, irrespective of the presence of multiple alleles. This variant of a gene generates an ample enzyme quantity, ensuring a surplus of a certain product within a cell, alongside encoding a functional protein. The coexistence of one dominant and one recessive allele for a gene culminates in an individual exhibiting the dominant phenotype. Within genetics, the concept of "dominance" delineates the process whereby a specific gene variant on one chromosome copy eclipses or prevails over the influence of another variant of the same gene on the complementary chromosome copy.

The ABO blood type serves as an example of codominance, particularly observed between the A and B alleles. Both are concurrently expressed in the phenotype, with neither holding superior dominance. However, both A and B alleles entirely overshadow the O allele, leading to the manifestation of the non-O allele's phenotype when one allele is O, and the other is anything other than O.

Incomplete Dominant Allele

In situations where neither of the two alleles exerts complete dominance over the other, or when the dominant allele fails to entirely suppress the recessive allele, the term employed is "incomplete dominance." The ensuing phenotype emerges as a distinct entity, divergent from both the dominant and recessive alleles, showcasing characteristics akin to a blend of both. When an organism's phenotype simultaneously expresses two heterozygous alleles, the outcome is incomplete dominance. This transpires as the unique phenotypes of each allele amalgamate, yielding a novel third phenotype. Partial dominance is another name for this phenomenon. The notion of incomplete dominance is crucial to understanding genetics because it describes how genetic and environmental factors interact to produce a novel phenotype or set of observable traits.

Cross-pollination studies between red and white snapdragon plants reveal partial dominance. The allele that creates the red color (R) is not fully expressed over the allele that creates the white color (r) in this monohybrid cross.

Difference Between Gene and Allele in Points

  • Function of the gene as codes that identify a certain trait, quality, or feature of an organism whereas allele contributes to a population's variation in a trait or characteristic.
  • Genes are present on specific chromosomal locations called loci, whereas an allele resides at the same locus as other alleles of the same gene.
  • Genes are Passed from parents to offspring during reproduction whereas alleles are Inherited from parents; individuals have two alleles for each gene from each parent.
  • Distinct qualities of an individual are influenced by distinct genes.In a population, a single gene might have many alleles, resulting in diversity in a trait.
  • A living thing's genetic makeup determines its traits and characteristics. Alleles play a part in the diversity and variance of traits within a population.

Conclusion

The molecular component of inheritance is thought to be a gene. The things we receive from our parents are therefore our genes. The genes' maximum level of expression is determined by alleles. Alleles therefore always exist in pairs. Some genes' traits are also determined by their alleles. Consequently, the major distinction between a gene and an allele is the changes they can produce in a trait.


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"Difference Between a Gene and an Allele." Diffzy.com, 2024. Mon. 17 Jun. 2024. <https://www.diffzy.com/article/difference-between-a-gene-and-an-allele>.



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