A homozygote is a type of zygote (cell that arises from the union of a male and a female gamete).
A zygote or zygote is a cell that arises from the union of a female gamete with a male gamete within the framework of the sexual reproduction of plants and animals. If a cell or organism has identical alleles of a gene for a certain trait, it is classified as homozygous (or homozygous ).
Although the concept of homozygote is not part of the dictionary prepared by the Royal Spanish Academy ( RAE ), the term is used to name the cell created by the union of gametes with the same genetic endowment or the organism from the union of gametes with these features.
The alleles and the locus
In a homozygote, the alleles at a locus are the same as the alleles on the homologous chromosome. In a heterozygote , however, the alleles of a certain locus are different on the homologous chromosomes.
To understand these ideas , it is important to know that alleles are versions of a gene . In other words: a characteristic can present itself in different ways, generating different alleles. The loci, on the other hand, are the sections where various genes are grouped together. Therefore, it can be stated that an allele is a variant of a genetic sequence at a specific locus.
Homozygous, in short, is a notion that is linked to the genetic composition of a certain characteristic in an organism . Each of the alleles of a gene is inherited from each parent: if the two alleles for a specific gene are the same, it is a homozygous or homozygous organism.
In a homozygote, the united gametes have the same genetic makeup.
Concept of homozygous from Mendel's work
In this context, the work carried out by the Catholic Augustinian monk named Gregor Johann Mendel is of great importance, which he published starting in 1865 in the form of a series of rules that we know today as Mendel's laws . These basically relate to the transfer of the characteristics of an organism to its successors that takes place in the phenomenon of genetic inheritance .
This discovery made by Mendel is considered a milestone in the evolution of the sciences of biology, so important that it is compared only to Newton's laws in the field of physics. This is because their studies were extremely precise and allowed scientists of the time to leave behind the superficial perspective that relied on blood mixing to explain genetic inheritance .
Mendelian laws
The first of Mendel's three laws states that if a dominant homozygote is crossed with a recessive one for a particular trait, the first generation of offspring will be composed of all individuals equal to each other, both from a phenotypic and genotypic point of view, and also phenotypically equal to the parent that has the dominant genotype, all this independently of the direction in which the crossing occurs.
With respect to Mendel's second law, it points out that throughout the formation process that gametes go through, the alleles are separated from their peers so that the determination of the genetic constitution of the so-called filial gamete takes place. Typically, a diagram called a Punnett square is used to represent the different hybridization possibilities. An organism inherits one homozygote or one heterozygote from each parent for each characteristic.
Depending on the criteria used by scientists, it is possible to simply speak of two Mendel laws. In this case, the third becomes the second. Its content is based on the independence of the characters transmitted between two generations. In other words, the traits are inherited independently of the others, that is, the inheritance patterns are different for each one.