What Is the Difference Between Co Dominance and Multiple Alleles?
Dominance may be a relationship between two alleles of 1 gene that affect the phenotype of 1 allele and masks the contribution of another allele.The trait which is expressed in a phenotype is called the dominant trait and the suppressed one is called a recessive trait. Incomplete dominance may be a sort of dominance where a trait incompletely dominates over the opposite and leads to an intermediate progeny.
Codominance
Co-dominance is the sort of dominance where the offspring show similarity to both the oldsters and it's thanks to the blending of alleles. When the F1 generation exhibits both the parental characters, this is often called codominance. The offspring will be a combination of both the parents. The ABO blood type system is one among the simplest samples of codominance. There are differing types of red blood cells like A, B, AB and O with or without the rhesus factor . The difference is within the antigen present on the red blood corpuscle surface which determines the precise blood type in an organism. For example: If an individual is blood type A, it means the RBC surface consists of antigen-A.But this is often decided by the gene I. The gene I even have three sorts of alleles namely, IA, IB and i. The alleles IA and IB produce two different antigens while the allele-i don't produce any antigen. Hence, allele i has dominance of alleles IA and IB over them.
As we know, two pairs of alleles have a diploid organism. Hence, in humans, there are two sorts of alleles of any combination. Depending on the mixture and dominance of the allele blood group of a private might be determined. The different combinations of alleles and their type of blood groups are given below.
Multiple Alleles
Mendel's work suggested that just two alleles existed for every gene. Today, we all know that's not always, or maybe usually, the case. However,individual human beings (and all diploid organisms) can only have two alleles for a given gene. Although, multiple alleles generally exist during a population level, and different individuals within the population may have different pairs of these alleles.
As an example, let’s consider a gene that specifies coat color rabbits, called the c gene. The C gene hasin total of four common alleles, namely, C, Cch, ch and C:
A CC rabbit has black and brown fur
A chh chh rabbit has chinchilla coloration
A ch ch rabbit has has Himalayan (color-point) patterning, with a white body and dark ears, face, feet, and tail
A cc rabbit is albino, along with a pure white coat.
Multiple alleles makes for many possible dominance relationships. In this case, the black C allele is completely dominant to all the others; the chinchilla c^{ch} allele is incompletely dominant to the Himalayan c^h and albino C alleles; and the Himalayan c^h allele is totally dominant to the albino C allele. Rabbit breeders found out these relationships by crossing different rabbits of various genotypes and observing the phenotypes of the heterozygous kits (baby bunnies).
FAQs on Co Dominance and Multiple Alleles Explained for Students
1. What are co-dominance and multiple alleles in genetics?
Co-dominance is a pattern of inheritance where two different alleles for a single gene are both fully expressed in the phenotype of a heterozygous individual. Neither allele masks the other. Multiple alleles refers to the existence of three or more alternative forms (alleles) of a single gene within a population, although any diploid individual can only possess two of these alleles at a time.
2. What is the most common example of co-dominance in the human population?
The most common example of co-dominance in humans is the ABO blood group system. The allele for blood type A (IA) and the allele for blood type B (IB) are co-dominant. If an individual inherits both alleles (genotype IAIB), their red blood cells will produce both A and B antigens on the surface, resulting in the AB blood type, where both traits are expressed equally.
3. Can you provide an example of multiple alleles found in animals?
A classic example of multiple alleles is the gene for coat colour in rabbits. A single gene (C) has four known alleles that determine the rabbit's coat colour. These alleles exhibit a dominance hierarchy:
C (full colour) is dominant over all other alleles.
cch (chinchilla) is dominant over Himalayan and albino.
ch (Himalayan) is dominant over albino.
c (albino) is recessive to all others.
4. How is co-dominance different from incomplete dominance?
The key difference lies in how the alleles are expressed in a heterozygous state. In co-dominance, both alleles are expressed independently and distinctly in the phenotype (e.g., a flower with both red and white spots). In incomplete dominance, the heterozygous phenotype is an intermediate or blend of the two parental phenotypes (e.g., a pink flower resulting from red and white parent flowers). Essentially, co-dominance is 'both expressed', while incomplete dominance is 'a mix is expressed'.
5. How does the ABO blood group system exhibit both co-dominance and simple dominance?
The ABO system is a perfect example of multiple genetic principles at work. Co-dominance is observed between the IA and IB alleles, as they are both expressed in an individual with the genotype IAIB. At the same time, simple dominance is shown in the relationship of these alleles with the i allele. Both IA and IB are completely dominant over the recessive i allele, meaning genotypes IAi and IBi result in Type A and Type B blood, respectively.
6. If multiple alleles exist for a trait in a population, why can an individual only possess two?
An individual can only have two alleles for any given gene because humans and many other organisms are diploid. This means we inherit one set of chromosomes from each parent. For a specific gene's location, or locus, there are only two corresponding spots in our entire genome—one on each homologous chromosome. While the population's gene pool may contain many different allele variations, any single individual can only carry the two that they inherited from their parents.
7. What is an example of co-dominance in plants?
Co-dominance is also observed in plants. For example, in some varieties of Rhododendron or Camellia flowers, crossing a plant with red flowers and a plant with white flowers can produce offspring with flowers that have distinct patches of both red and white. This is not a blended pink (which would be incomplete dominance), but rather the simultaneous and independent expression of both the red-petal allele and the white-petal allele in the same flower.
