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In biology, the terms dominant or dominant characteristic are frequently used. The broad definition of dominant is “in command.” Other definitions include commanding conduct, being powerful, and having the upper hand over others. It may also refer to having power or influence over anything else. The term “dominant” is most commonly used in genetics and ecology, two disciplines of biology.
In genetics, the term “dominant” refers to an allele or a gene that is expressed in an organism’s phenotype, concealing the influence of the recessive allele or gene when it is present; it may also refer to a feature or character that is expressed over one that is not. In ecology, it refers to an individual or group of species that has the most impact or power over other organisms in its ecological community. It refers to the typical propensity for one side of the body or one of a pair of organs to dominate or be utilised more consistently than the other in anatomy and physiology.
Dominant derived from the French dominant, which is derived from the Latin dominant-domin (us), which means “master” +-ant.
What is Dominant?
The features that arise in the following generation of a species are known as dominant traits in genetics. A dominant allele is passed down from one generation to the next. The phenotype refers to the observable features or traits, whereas the genotype refers to the genetic component that determines the trait. A gene is defined as dominant when it is prevalent in a population, meaning it is commonly passed down from generation to generation. The term dominant, on the other hand, refers to the connection between alleles in this context.
Alleles are gene variations by definition. G.J. Mendel was the first to establish the notion of dominance in 1860. He established the ideas that subsequently became the rules of Mendelian Inheritance, albeit without using the names gene, allele, phenotype, and so on. The Law of Dominance is one of these laws.
In essence, one allele is dominant and the other is recessive when the gene determining a trait is heterozygous, meaning the alleles are not the same. The dominant gene variation (allele) is more highly expressed than the recessive gene variant (allele). As a result, the dominant allele is considered the dominant allele, whereas the recessive allele is considered the recessive allele. A capital letter represents the dominant allele, whereas a lowercase letter represents the recessive allele.
Mechanism of Dominance
Sexually reproducing animals contain two sets of chromosomes. Humans have 46 chromosomes in total, with 23 pairs on each chromosome. An elephant has 56 chromosomes, while a monkey has 48. Thousands of genes are found on these chromosomes. The genes contain the instructions for making proteins.
The code contains all of the information about how the protein should evolve, as well as the traits and qualities that it should have. As a result, liver protein is distinguished from muscle and kidney proteins. Proteins differ not just on a molecular level, but also in structural features such as structure, shape, and size, as well as physiological qualities.
On a single chromosome, there are thousands of genes. In most cases, a chromosome contains at least two copies of each gene. The positions of these gene copies (alleles) on a chromosome are identical (called locus). They are placed together because they are in the same position.
Take the ear lobe characteristic, for example. There are two gene variations for it: one that causes a detached earlobe trait and the other that causes an attached earlobe trait. These alleles are found in pairs. One allele is inherited from the mother, while the other is inherited from the father. When we state that a gene is dominant, we are referring to a certain allele. The dominant allele is dominant, whereas the recessive allele is recessive.
As previously stated, the dominant allele is denoted by a capital letter, therefore in this case, we’ll use the letter “F” to denote the dominant allele for the dominant characteristic, which is the free-hanging earlobe. The recessive allele responsible for the connected earlobe characteristic (recessive trait) will be indicated by a tiny letter, which in this case is “f”. When one of the parents has a pair of free-hanging earlobes, and the child has the same earlobe feature, the parent’s allele was dominant.
A specific phenotype is produced by the dominant allele (observable changes in physical characteristics). Protein functions are best expressed by a dominant allele. Because the dominant copy of the gene generates enough enzymes to provide a cell with the necessary material and code, this is the case. As a result, the dominant allele-controlled cell has the same characteristics as the dominant allele-controlled cell.
Furthermore, the dominant and recessive behavior of genes is only a description of the interaction between the two alleles; in fact, the interactions are far more complicated. A dominant allele might be dominant over one allele while being recessive for others. It is dependent on the type of protein and how they interact.
For example, a polygenic characteristic is regulated by multiple genes that, when turned on, are produced as a unit, rather than merely two alleles of a single gene (monogenic). Polygenes are many genes that regulate a single characteristic; polygenic traits in humans include eye colour, hair colour, and skin colour. Polygenic characteristics are more frequent in people than monogenic features. Other monogenic characteristics in humans include widow’s peak, hitchhiker’s thumb, and colour blindness, in addition to the earlobe trait.
When an allele is entirely dominant, the consequences of the recessive gene are usually completely hidden. Complete dominance can be found in heterozygous individuals in particular (those that have two different alleles at a locus, e.g. sickle cell trait). The two alleles that make up a pair in a homozygous organism are identical. As a result, a homozygous dominant for a characteristic would have the same coding, resulting in the same protein. Both alleles are recessive in a homozygous recessive creature, and because there is no dominant gene to conceal their impact, the recessive characteristic will appear.
There are several instances where dominance is insufficient. The dominant alleles generate distinct enzymes in such instances. However, none of the genes outweigh the natural characteristics. Physical effects are produced in equal amounts by both alleles. The Punnett square below, for example, depicts a cross of two red and white flowers. Pink is the resulting colour. It’s important to note that incomplete dominance impacts a wide range of enzymes, not only colours.
A codominance of alleles can occur in various circumstances. However, in codominance, both alleles are expressed in their separate regions. A red cow, for example, has red coat alleles, whereas a white bovine has white coat alleles. When both alleles are present in the same cow, the outcome is a coat with red and white spots. Allele codominance has been seen in dogs and cats, resulting in a broad range of coat and colour patterns.
In genetics, the dominant allele is the allele that defines an organism’s phenotype. Its impacts are more easily detected than recessive influences. The dominant allele in a monogenic trait is indicated by a capital letter, whereas the recessive allele is represented by a small letter, such as Aa (where “A” refers to the dominant allele and “a” to the recessive allele).
Dominant in Ecology
In ecology, the term dominant refers to the degree to which one species outnumbers its competitors in terms of population, production, and size in the ecosystem. Temperature, humidity, groundwater conditions, and the existence of animals that feed on selected plants all have a role in species dominance in the ecological environment.
To ensure that the species’ generation survives and reproduces, they seek a suitable habitat. To maintain their dominance, certain species can alter their surroundings in a variety of ways. During the winter, many birds and animals move from colder climates to warmer ones. This habit also allows them to maintain their ecological dominance over other species.
A dominant in ecology is an entity, such as an animal, that rules over a social hierarchy and is generally the top predator with the best access to food, territory, and mates.
Dominant in Other Areas
The term dominating is sometimes used to describe one person’s behavioural domination over another. In ethology (the science of animal behaviour), dominance is characterized as one individual having preferred access to resources over another. In anthropology, dominance refers to possessing a greater social standing than others, with other individuals responding to the dominating species in a subservient manner.
The advantage of this type of domination is that the dominating individual has access to food or prospective partners without having to engage in combat with another person. Dominance in anatomy and physiology refers to the natural propensity for one side of the body or one of a pair of organs to dominate or be utilised more consistently than the other, such as right-handedness vs. left-handedness.
Below are some instances of dominant characteristics, genetics, and ecology.
i. Dominant Examples in Genetics
There are a number of characteristics in human genetics that are governed by dominant alleles.
When compared to other eye forms, such as round eyes, almond-shaped eyes are a dominating feature in humans.
The majority of people have detachable earlobes, whereas just a handful have connected earlobes. As a result, the allele for detached earlobe is dominant.
The allele that causes people to be right-handed is dominant over the one that causes them to be left-handed. Furthermore, right-handed people outnumber left-handed people in the population.
A dominant allele results in the development of six fingers rather than five. Polydactyly is the condition of having an additional finger (or toe). Mutations in the GLI3 gene on chromosome 7 have been linked to a variety of diseases in humans, one of which is polydactyly (e.g., preaxial polydactyly IV, postaxial A1, etc.)
The brown hue of the eyes takes precedence over the blue. However, it’s important to note that eye colour is a polygenic characteristic, not one regulated by a single gene.
Selective breeding and genetic engineering approaches have been used to promote desirable dominant characteristics, such as crops with dominant alleles that give superior disease and drought tolerance. When using these approaches, however, caution should be exercised since they may result in the transfer of characteristics to other species, such as weeds obtaining the desired feature and outgrowing essential crops. As a result, scientists must investigate the good and negative effects of selective breeding.
ii. Dominant Examples in Ecology
The following are some instances of dominance in ecology:
1. White polar bears dominate the Arctic because they can withstand extreme cold, whereas brown bears dominate Asia, Europe, and North America since their habitats are comparably warmer.
2. In temperate bogs, sphagnum (a moss) is the dominating plant.
3. Tidal wetlands in tropical areas are dominated by mangrove species.