He Dominant gene and the recessive gene Can be defined as the DNA sequence that makes it possible for certain characteristics and physical traits to be inherited by people.
They are responsible for carrying the genetic information that both males and females can pass to their offspring.
The organization of genetic type of organisms is known as genotype. This is responsible for affecting the physical features and in some cases the behavior of individuals of all species.
The genotype is composed of alleles or genes contained in each chromosome. Each allele is responsible for carrying a characteristic related to the traits of the individual.
When two alleles of different characteristics are found, they give rise to the formation of a heterozygous gene, however, when two alleles of the same characteristics are found, they give rise to the formation of a homozygous gene.
Thus, when two alleles of the same gene - whose characteristics are different - are united, these can be of a dominant or recessive character.
That is, the traits of individuals may have more or less possibilities to develop in one way or another (Hartl & Ruvolo, 2011).
Dominant gene
The dominant gene is one that is present both in the mother and the father and therefore appears twice in the genotype of the children.
In this way, it can be said that appears twice as much in the genetic configuration of the children and therefore is more likely to develop.
However, in the case of humans, individuals have double or diploid chromosomes. This means that genetic information is divided into two parts, one that comes from the mother and the other from the father (Porto & Gardey, 2010).
In the case of dominant genes in humans, they may be present only in one of the progenitors, and yet they are likely to manifest in the traits of their offspring.
In this way, it can be said that for a dominant gene to be transmitted and manifested only it is necessary for one of the parents to inherit it to its children.
One way to illustrate this situation is in the color of the eyes of humming beings. The coloration of the eyes depends on several genes, each of these genes has several alleles, ie several points on the chromosomes where the information is encoded.
This is how the color of a person's eyes depends on how the involved alleles are combined within the definition of this trait.
For this reason, brown eye color may conceal blue eye color, since their genes are usually expressed more strongly in alleles of different chromosomes. In general, when a gene manifests itself with greater intensity is said to be dominant.
Not all degrees of dominance are the same. In the case of a gene that has three alleles (A, B and C), it can be that B is dominant in relation to C.
However, A may be dominant over B and C. In this way, the alleles in B and C will never manifest in the presence of A, and those of C will never manifest in the presence of B.
Gen recessive
Contrary to the dominant gene, the recessive gene is one that will present with less intensity in the traits of the individuals. This is how the recessive gene can only appear in the offspring when both parents carry it and transmit it to their children.
The recessive gene is distinguished because in the presence of the dominant gene can not be manifested. Thus, in order to be able to express themselves, two copies of the same must be collected, one from the mother and the other from the father (Portela, 2017).
To illustrate the meaning of the recessive gene we must return to the example of eye color in humans. Clear eyes can only be manifested if both parents have the recessive gene that allows inheritance of this characteristic.
It is important to mention that there are many diseases that can be carried in a recessive way and are only manifested in the children when both parents transmit them.
Some of the diseases most commonly inherited in recessive genes may be Wilson's Disease, Hereditary Spherocytosis and Hemochromatosis.
Although these diseases do not manifest in children, the genes that carry their coded information will be carried by them in a recessive way.
Thus in the first generation of offspring the disease may not manifest itself, but it may appear in the third generation if it is paired with another individual who also carries it.
Chromosomes
The genome or set of genes of living beings is broken down into multiple molecules called chromosomes. The more complicated the genetic structure of a living organism, the more chromosomes it will have.
For example, humans have 46 different chromosomes, or 23 double chromosomes (Utah, 2017).
Within the chromosomes are located all the genes and alleles. For example, within the chromosomes of humans is a pair dedicated to determine the sex of the offspring (XX for women and XY for men).
This characteristic is defined by the father, since this is the only one that has the ability to contribute a Y chromosome to the offspring.
Example of dominant and recessive gene
Baldness or androgenic alopecia is an example of a recessive gene. This is determined by a gene located on the X chromosome, made up of two alleles.
One of these alleles, called the G allele, produces baldness and the other (allele A) does not produce it. Being the allele A is dominant over the G.
Men require more than one G allele to become bald, since the gene is located on the X chromosome and therefore can not be masked with an allele A.
On the other hand, even if a woman has only one G allele, she will not become bald if the other allele is A. In this sense, women need to carry both G alleles to develop alopecia (VAIVASUATA, 2015).
References
- Hartl, D.L., & Ruvolo, M. (2011). Burlington: Jones & Bartlett Learning.
- Portela, R. (2017). Science and Biology . Retrieved from"What is a dominant gene and a recessive gene?: cienciaybiologia.com
- Porto, J.P., & Gardey, A. (2010). from . Obtained from DOMINANT GEN DEFINITION: definicion.de
- Utah, U. (2017). Genetics . Retrieved from"What are Dominant and Recessive?: learn.genetics.utah.edu"
- (November 10, 2015). biology . Differential between dominant and recessive: difference between.info.