Mono-hybrid Crosses

Mono-hybrid crossing is a crossing, for which characteristic is the difference of the parental forms from each other according to the available one pair of alternative, contrasting features. An attribute is any feature of the body, any of its properties or quality, according to which it is possible to distinguish individuals. For plants, such a property is, for example, the shape of the corolla (asymmetric or symmetrical), its color (white or purple), etc. Characteristics include the rate of maturation (late ripeness or early ripeness), as well as resistance or susceptibility to certain diseases .

All properties in the aggregate, beginning with external and ending with certain features in the functioning or structure of cells, organs, tissues, are called a phenotype. This concept can also be used in relation to one of the available alternative signs.

The manifestation of properties and attributes is carried out under the control of existing hereditary factors - in other words, genes. Together, genes form a genotype.

Mono-hybrid crosses according to Mendel are represented by crossing peas. In this case, there are such well-marked alternative properties as white and purple flowers, green and yellow color of immature beans, wrinkled and smooth surface of seeds and others.

Conducting a mono-hybrid cross, G. Mendel, an Austrian botanist of the 10th century, found out that in the first generation (F1), all hybrid plants had flowers of a purple hue, while the white color did not appear. Thus, Mendel 's first law on the uniformity of first generation samples was derived. In addition, the scientist established that in the first generation all samples were homogeneous and for all seven traits studied by them.

Thus, a mono-hybrid cross involves for individuals of the first generation the presence of alternative signs of only one parent, while the properties of the other parent seem to disappear. The predominance of properties G. Mendel called dominance, and the signs themselves are dominant. The scientist called the qualities that are not manifested as recessive.

Conducting a mono-hybrid cross, G. Mendel subjected self-pollination to the grown hybrids of the first generation. Formed in them seeds the scientist sowed again. As a result, he received the following second generation (F2) hybrids. In the obtained samples, cleavage was observed on alternative grounds in an approximate ratio of 3: 1. In other words, three quarters of individuals of the second generation had dominant properties, and one quarter - recessive. As a result of these experiments, G. Mendel concluded that the recessive trait in the samples was suppressed, but did not disappear, appearing in the second generation. This generalization was called the Law of Splitting (Mendel's second law).

The scientist pursued further mono-hybrid interbreeding in order to reveal how succession will occur in the third, fourth and subsequent generations. He grew the samples using self-pollination. As a result of the experiments, it was found that plants, the characteristics of which are recessive (white flowers, for example), in subsequent generations reproduce the offspring only with these (recessive) properties.

The plants of the second generation, whose properties were named by G. Mendel as dominant (owners of, for example, purple flowers) behaved differently. Among these samples, the scientist, analyzing the offspring, identified two groups with absolute external differences for each specific feature.

For individuals that differ in two features, a dihybrid cross is used . The tasks for determining genotypes and phenotypes are comparatively simple, when they are solved, Mendel's laws are applied.