When studying Genetics, some terms appear frequently and are extremely important for understanding some processes. One of these terms is the allele, a concept which refers to the differences between the genesis that is directly linked to two other important points of genetics: homozygous and heterozygous organisms.
→ What are alleles?
You alleles they are the alternative forms of a given gene and occupy the same locus on homologous chromosomes. When we refer to locus, we are talking about the position of the gene on the chromosome; when we talk about homologous chromosomes, we are referring to chromosomes that have genes for the same trait.
In diploid organisms, such as humans, chromosomes come from the parents, one group coming from the mother and the other from the father. Analyzing the genes of an individual, we can see, for example, that in homologous chromosomes from the mother there may be a gene A for a given characteristic, and in those coming from the father a gene to. despite A and a
being the same gene, they present themselves modified, causing some alterations for the same characteristic. Therefore, A and a are the alleles.It is important to note that alleles are always represented by letters. The allele is represented by a lowercase letter when it is recessive, that is, when it is expressed only in pairs (Ex.: aa). already the allele dominant it is represented by a capital letter and is expressed even in a single dose (Ex.: AA or Aa).
Note that in homologous chromosomes there are alleles for the same trait occupying the same locus
→ What is homozygous?
is called homozygous, or pure, that individual who has a characteristic determined by equal alleles. Based on the gene A example, a homozygous individual can be either AA or aa. In these cases, it is possible to see that the individual has only one type of gamete, that is, if a man is AA, his sperm will carry the A allele.
→ What is heterozygote?
is called heterozygous, or hybrid, the individual who has a certain characteristic conditioned by two different alleles. Thus, for gene A, a heterozygous individual can be represented by Aa. In this case, two types of gamete, that is, if the individual in question is an Aa male, he will be able to produce sperm that will carry the A allele or the allele The.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-alelo.htm