What is heterosis in biology and the application of its effect?

Each summer resident or gardener knows what isheterosis. Another thing is that often we simply do not correlate this biological concept and the effect it produces with this complex word. Although in the fundamental scientific environment disputes are still being made about the mechanisms and the effect of heterosis, the average person has long used it in everyday life. In this article we will try to explain intelligently and understandably what is heterosis, what effect it causes and how it is used in human economic activity.

Academic knowledge

Heterosis is in biology the phenomenon of "strengthhybrids ", namely the increase in viability, rapid growth and larger sizes of hybrids in the first generation in comparison with the parent organisms. Filial 1 or F1, as the descendants of the first generation are designated, if the parents were not of the same species, they may have the effect of heterosis, or it may be that there will not be one. In subsequent generations, changes do not occur. The effect of heterosis is not always useful for a particular organism. As is known, hybrids are often low-fertile (the ability to reproduce prolific progeny) up to infertility.

History of discovery

What is heterosis, namely, the amplification of hybrids,knew before the laws of Mendel's inheritance. The term was introduced in 1914 by the American biologist W. Schell. But back in 1765, the Russian naturalist and biologist I. Kelreiter first described the hybrid power of the descendants of makhorka and paniculose tobacco obtained by artificial cross-pollination of plants. And Charles Darwin even wrote a separate work on the power of hybrid forms - "The action of cross-pollination and self-pollination in the plant world" (1876). Hybrid maize seeds in bulk were obtained by D. Bill at the Michigan Agricultural College as early as 1878.

Mechanism: complementation or over-domination

What is heterosis in terms of its mechanisms - and today the question. In the environment of competent scientists, there are two theories about the mechanism of this phenomenon:

• The theory of complementarity explains the phenomenonamplification of hybrids by "inclusion" of genes that were in parental forms in a homozygous (aa or AA) state. In the first generation of hybrids, the heterozygous gene allele (Aa) causes heterosis.
• The theory of overdominance. According to this version, heterosis is caused by an increased dominance of dominant alleles in hybrids and disconnection of repressors (oppressors) of genes. A key role is played by the gene hierarchy theory, according to which there are key regulators in the genome - genes that play an important role in the inclusion of certain genes.

Recent studies of molecular biology,however, prove the presence in heterosis hybrids of mechanisms and complementation, and overdominance, and the presence of key "switches" of genes that order music in the genome orchestra.

Types of heterosis

There are the following types of this phenomenon:

• Reproductive form, in which there is an increase in fertility and better development of reproductive organs, seeds or fruits.
• Somatic heterosis is caused by coincidence of alleles and a large development of vegetative and somatic organs.
• The adaptive form helps to increase the viability and stability of hybrid organisms.

Heterosis in nature and human economic activity

In nature, inter-species closely relatedcrossing originated with sexual reproduction. And in evolutionary teaching there is even one way of speciation - hybridization. Man has been using the effect of heterosis since time immemorial. For example, hybrids of a horse and a donkey (or one-horned camel) are known for their strength and increased endurance. Hybrid form "bister", obtained from crossing of beluga and sterlet, is actively used in aquaculture, as it grows faster than parental forms. In plant growing, we have long switched to hybrid crop production. The productivity of hybrids of maize, onion, tomato, cucumber and bell pepper is 25% higher than the clean lines (on the seeds is denoted by the symbol "F1").

Heterosis in humans: jeremi and mongi

The effect of heterosis manifests itself in interracialmarriages. This topic is rather delicate, especially in the context of pseudo-scientific speculation on the degeneration of the nation and other populist statements. But geneticists and molecular biologists unequivocally state that heterosis is caused by interethnic marriages with the same mechanisms, and the general biological parameters of the offspring can be higher than the parent ones. When the effect of heterosis appears (which is more likely with the purity of national characteristics in parents), people are called the word "jer" from GeteRozis, GR. If the effect of heterosis is not manifested, the overall parameters of the children will be worse than the parent ones. Such people are called "Mong" from MONGrel.

And finally

For humanity, the last 100-150 years of steelyears of development of transport communications and migration of the population, destruction of class, religious and ethnic obstacles. This led to the mixing of nations and nationalities, interracial and interethnic marriages. And maybe it is the effect of heterosis in biology - this is an increase in population growth in most countries by 5-15 cm and the onset of puberty by 13-14 years instead of 16-18 just 100 years ago?