Dihybrid Abbreviations

The dictionary of the Royal Spanish Academy ( RAE ) does not recognize the term dihybrid. However, the concept is used in biology to name the one or that that originates from the crossing of two organisms with dissimilar characteristics.

This crossing gives rise to a diploid being that, in its nucleus, has two sets of chromosomes that are homologous. The dihybrid gene pair may be on separate chromosomes or on the same chromosome.

A dihybrid, in short, arises from the crossing of races differentiated by pairs of allelomorphic characters. As the characters segregate independently, they can lead to the appearance of new combinations.

The crossing of two organisms with different characteristics generates a dihybrid.

Mendel and the concept of dihybrid

The notion of dihybrid was developed by Gregor Mendel (1822-1884), father of Mendelian genetics and creator of the so-called Mendel’s laws. Through these postulates, which explain how the characteristics of parents are transmitted to offspring through genetic inheritance, the scientist showed, among other things, how dihybrids are generated.

Mendel’s Second Law, also known as the Law of Independent Segregation of Characters, states that when varieties of organisms that differ by two characters are crossed, each of the characters is transmitted independently. Therefore, in the formation of a gamete, each allele is separated from the other of its pair for the determination of the genetics of the offspring.

In this framework, a dihybrid arises when two monohybrids act independently. Mendel came to his conclusions by studying the crossing of yellow, smooth seeds with green, wrinkled seeds, analyzing the successive generations.

By monohybrid we understand a strain, organism, or individual that is heterozygous (formed when two sex cells of different genetic endowments unite) for only one particular trait, or for a single locus (a position on a chromosome that does not change ). and determines that of a genetic marker or a gene) or trait of the gene that is taken as a reference.

Gregor Mendel was the one who developed the concept of dihybrid.

The experiments

The first experiment that Mendel carried out, in fact, was the so-called monohybrid cross, mentioned above, for which he used two plants that coincided in their genetic endowment but had only one different character: the color of their seeds. The purpose of the scientist was to discover how later generations would inherit this character.

Regarding the dihybrid cross, we can say that it involves individuals heterozygous for two loci (the plural of locus, pronounced /loki/ ); in other words, their genotypes have two different alleles at each locus. If these are biallelic (as might be the case with A, a and B, b ), then AaBb is the dihybrid genotype.

Types of gametes generated by dihybrids

Dihybrids generate four types of gametes, and the difference between them is that each one has a different pair of alleles (for each loci of the pair, it gets one). In the example of the previous paragraph, the result would be the following: the production of gametes AB, Ab, aB and ab. Given that the distribution of the alleles occurs arbitrarily among the gametes, according to the law of independent segregation, for a locus X, fifty percent of the gametes will be of type X and the rest, of type x.

On the other hand, given that the combination of the alleles occurs independently, there is the same degree of probability that the A and a combine with the B and with the b, that is, that the four types of gametes previously exposed appear with equal frequency. When crossing two dihybrids, an offspring is obtained that, if it has sufficient dimensions, presents all the possible genotypes when uniting two gametes at random.

List of Acronyms Related to Dihybrid