Complementary genes: Definition, Meaning Types, Examples, Causes, Explanation

What Are Complementary Genes?

Duplicate genes are genes that are similar in function and responsible for the manifesting of a specific phenotype. Dominant alleles in either gene of the pair are necessary to produce the trait; however, the trait can be masked if a recessive allele is present in the individual’s genotype. This concept is useful in genetic and heredity systems as it is necessary for understanding how some characters are inherited and also the roles of genes and diverse phenotypes. This article will define complementary genes explain their roles in genetic inheritance processes and give an impetus to other related uses.

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Basic Concepts Of Genetics

The genetics related to this topic involve the basics of:

Genes And Alleles

They are segments of DNA that contain information relating to protein synthesis or RNA molecules that are important for different activities in living organisms. Alleles are different forms of a given gene due to mutation occurring in the gene locus. For instance, the genes governing eye colour could have several alleles, blue alleles or brown alleles.

Dominant And Recessive Traits

Expressed traits are those that result when any dominant allele is present in the genotype irrespective of the presence of the other alleles. Such alleles and hence such traits are those that are expressed only where the individual inherited two alleles and both are of the recessive category. For instance, the brown-eyed allele is dominant over the blue-eyed allele and unless they inherit two recessive alleles, they are blue-eyed.

Gene Interaction

Epistasis can be defined as the phenomenon whereby the action of one gene depends on what alleles of one or many other genes are present. This interaction modifies the outlook of traits in a manner that cannot simply be conferred by the direct results of either gene making a relatively complex task in genetics.

Types Of Gene Interaction

Gene interaction can be classified as:

Epistasis

It can affect the function of another gene or hide its abnormalities. For instance, in Labrador retrievers, pigment deposition is dictated by the E gene, while the contributing factor in colour (either black or brown) is the Bgene. It was further found that the recessive e allele at the E locus will be able to mask the effect of the B gene, thus the dog will have a yellow coat despite the presence of the B allele.

Complementary Genes

That is, both genes will have to have a minimum of one dominant allele to exhibit a certain phenotypic feature. For instance, in sweet peas, the gene responsible for flower colour is controlled by the activity of two genes. The classification of the genotypes making up the flowers shows that only if both genes possess dominant alleles, then the flower coloured; otherwise, the flower is white.

Duplicate Genes

Holo gene is when two genes are involved in a trait and one of them has a dominant allele, the trait is displayed. This means that if one gene of each pair contains an A1 or a B1 allele, an organism will display the first manifestation of the trait.

Importance Of Gene Interaction In Phenotypic Expression

Gene interactions hold a central position in providing an account for the phenomenon of multiple shape-regulatory genes. On this, they can help explain why traits do not always exhibit the basic Mendelian distributions of traits and can offer an explanation of why there are differences in the variations of traits in diverse individuals and populations. Therefore, through such interactions, researchers can get enhanced estimates of the probable genetic results, originate the fundamental idea of genetic ailments, and investigate the progression of certain traits.

Complementary Genes

• These are genes that cooperate in an organism to produce specific phenotypes.

• This is because two complementary genes are known to collectively bring about a certain characteristic of an organism.

• Only when there is at least one dominant allele for each gene will express the given trait.

• Due to this rather stringent requirement, the participant gene is chosen carefully.

• This means that in a given population, for the absence of a particular trait, both genes must possess only recessive genes.

• This interaction shows how a simple phenotypic change can be controlled by several genes which all in all have an equal efficacies.

Mechanism Of Action

• In the case of complementary genes, the two genes work simultaneously in forming the whole phenotype.

• The alleles of both genes must be present, which makes the particular characteristic observable.

• If one gene has only recessive alleles it does not allow the expression of the trait no matter what alleles are present in the other gene.

Example: in sweet peas, two genes control flower colours which stands for colour P genes for pigment production. Both genes require a dominant allele for colouration in the flowers to be coloured Necessitating a least dominant allele. If either of the genes is absent that is cc or pp then the flowers will be white. This discussion portrays how the complementary genes cooperate and how their end product is developed with the final colour of flowers.

Examples Of Complementary Genes

A few examples of complementary genes are:

Flower Colour In Sweet Peas

Hoping to resolve the controversy over flower colour inheritance, William Bateson and Reginald Punnett did experimental breeding on sweet peas or Lathyrus odoratus. The investigators hybridized plants with two different fluorescent colours and had very young students describe the progeny.

Explanation of the Results: The allelic tests and interactions revealed that the quality of the colour and pigment of the sweet peas’ flowers depends on two genes: C and P. For colour to show in the flower, the genotype of that particular flower should be PpCc Since C_P_ genes are incompletely dominant, one dominant allele is required for both genes to show colour. If both are cc or pp, the flowers are white While both genes are heterozygous dominant (Cc or Pp), the flowers are pink. This illustrated the situation where two distinct genes, could only manifest this trait if they were both dominant.

Coat Colour In Mice

Description of the Genes Involved: In mice, coat colour is controlled by pairs of complementary genes. Here, one gene, ‘A’ is responsible for synthesizing pigment and gene ‘B’ is involved with the placement of the pigment.

Interaction and Phenotypic Expression: For a mouse to have the specific coat colour there must be the presence of the dominant alleles in both these genes (A_B_). If either gene is homozygous recessive (aa or bb), the pigmentation process is said to be aborted, and there is the said lack of the colour expected. This outlines how alleles that are located on two different chromosomes work together to make coat colour contingency.

Other Examples In Plants And Animals

Corn Kernel Color: In corn the colour of kernels can be determined by complementary genes is also a possibility. For instance, the alleles in two genes involved in the determination of pigment synthesis and its distribution produce different kernel colours if both are dominant.

Flower Color in Petunias: In petunias, it is the complementary genes that control the flower colouration of the flowers. The combination of the genes relevant for colour production and colour development yields a palette of colours when both genes are homozygous individual possesses only recessive alleles while a heterozygous individual as defined by Griffiths, is one whose genotype includes at least one dominant allele. The flowers will be white if at least one of these genes is recessive. as the hypothesis used in this cross-appropriates the genes of dominant and recessive traits.

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