Genetics: It is the study of the nature, organization, expression, transmission and evolution of the encoded genetic information of organisms that is transmitted from one generation to another.Gene: It is the structural and functional unit of inheritance that determines the biological characteristics of an individual. It is about each of the hereditary factors of a character that is transmitted from parents to children.
Locus: Specific site or place that each gene occupies on a chromosome. A given gene always occupies the same locus on the same chromosome.
Character: It is any characteristic transmitted by the genes that is observable in the individual. The color of the flowers, the type of hair or the shape of the fruit are characters.
Genotype: It is the set of all the genes that an individual possesses, that is, inherited from their parents and that remain unchanged throughout their life. The genotype, together with environmental factors that act on genes, determines the characteristics of the organism, that is, its phenotype.
Phenotype: It is the physical manifestation of the dominant genes in the individual, which is determined by the genotype and the environmental conditions in which the individual lives. In essence, it is about any observable characteristic or trait of an organism, such as its morphology, development, biochemical properties, physiology, and behavior.
Allele: It is each one of the members of a pair of genes that occupies the same locus in a pair of homologous chromosomes and that encodes the same character. In other words, it is each of the alternatives that a gene presents.
Dominant allele: It is the allele that manifests phenotypically and dominates the recessive allele. It is represented by a capital letter.
Recessive allele: It is the allele whose character is masked by the action of the dominant allele. It is represented by a lowercase letter.
Lethal alleles: They are those that cause death at the level of the gamete or at the level of the zygote, and it may then happen that the individual does not come to be born or that he dies before reaching reproductive capacity. Lethal alleles are usually recessive, so they only manifest under homozygous conditions.
Homozygous or pure race: It is an individual who for a character has two equal alleles, either dominant or recessive. It is represented by two equal letters, either uppercase or lowercase: AA, aa, BB, bb.
Heterozygous or hybrid: It is an individual who has two different alleles for a character, one dominant and the other recessive. They are represented by two equal letters, one uppercase and one lowercase: Aa, Bb. If an individual is a hybrid for one character, it is called a monohybrid, if it is a hybrid for two characters, a dihybrid, and if it is for three, a trihybrid.
Codominance: Situation in which when two different homozygous individuals hybridize, the phenotypic characteristics of both parents appear at the same time in the descendant individuals. It is a type of complete dominance in which both characters are expressed.
Intermediate inheritance: Situation in which when crossing two different homozygous individuals, in the offspring the characters are manifested as a mixture of the phenotypes of the parents. It is a type of incomplete dominance in which an intermediate character is manifested to that of the parents.
Sex-linked inheritance: It is the inheritance related to the pair of sex chromosomes. The X chromosome carries many genes, but the Y chromosome only a few and the majority in relation to masculinity. The X chromosome is common for both sexes, but only the male has a Y chromosome. Genes linked to one chromosome or another determine the inheritance of certain characteristics, mutations or diseases in men and women.
Multiple allelism: It occurs in those genes in which there are more than two different alleles in the population for that gene. An example of this is the AB0 system that controls the inheritance of blood groups in humans.
Polygenic inheritance: It occurs when the expression of a character is due to the action of more than one gene that may also have more than two alleles, which gives rise to a wide variety of phenotypes.
Backcrossing: It is a cross used in cases of dominance to find out if an individual is hybrid or purebred. It consists of crossing the problem individual with a homozygous recessive individual. If heterozygous individuals appear, the problem individual will be a pure race, and if homozygous recessive individuals appear, the individual will be a hybrid.
The following video reviews some of the most important concepts in this list. If you still have doubts, take a look!
You can read the Spanish version of this glossary here.
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