such thing as the inheritance of characteristics, widely studied in genetics.This explains the similarity of their offspring and parents.Curiously, some manifestations of inherited traits in common.This phenomenon was first described in detail scientist T. Morgan, was called "linked inheritance."We'll talk more about it.
As you know, every organism has a certain number of genes.Chromosomes as in this case - is also strictly limited number.For comparison, a healthy human body has 46 chromosomes.Genes as it is a thousand times more.Judge for yourself: each gene is responsible for a particular trait, manifested in the appearance of a person.Naturally, a lot of them.Therefore we began to say that several genes are localized to a single chromosome.These genes are called linkage groups and define linked inheritance.Such a theory is vital to the scientific community for a long time, but only T. Morgan gave her definition.
Unlike the inheritance of genes, which are located in different pairs of identical chromosomes linked inheritance causes the formation digeterozigotnoy individual of only two types of gametes, repeating a combination of parental genes.
Along with this, there gametes, the combination of genes that differs from the parent chromosomes.This result is a consequence of the crossover - the process, the importance of which in genetics is difficult to overestimate, because it allows the offspring to receive a variety of symptoms from both parents.
In nature there are three types of inheritance of genes.In order to determine what type it is inherent in the art of the pair used test cross.As a result, it is sure to get one of the three options below:
1. Independent inheritance. In this case, the hybrids are different from each other and from the parent in appearance, in other words, as a result, we have 4 different phenotypes.
2. Full adhesion genes. first generation hybrids were obtained by crossing the parental species, are the same phenotype indistinguishable parents and each other.
3. Incomplete adhesion genes. Just as in the first case, when crossed turns Class 4 different phenotypes.At the same time, however, the formation of new genotypes, completely different from the parent fund.It is in this case the formation of gametes crossover intervenes as mentioned above.
also found that the smaller the distance between the inherited genes in the parental chromosome, the more likely they are fully linked inheritance.Accordingly, the farther apart they are located, the less often crossing occurs during meiosis.The distance between genes - a factor that primarily determines the likelihood linked inheritance.
also necessary to consider the linked inheritance associated with the floor.The essence of it is the same as in the embodiment discussed above, however, inherited genes are in this case located in sex chromosomes.So talking about this type of inheritance is possible only in the case of mammals (man among them), some reptiles and insects.
Taking into account the fact that XY - a set of chromosomes corresponding to the male sex, and XX - women, we note that all the main features of which are responsible for the vitality of the body, are located in a chromosome present in the genotype of each organism.Of course, we are talking about the X - chromosome.In females may be present as the recessive and dominant genes in the chromosomes.Men may also inherit only one option - that is, either the gene manifests itself in the phenotype or not.
Linked inheritance due to gender, often heard in the context of the disease which is characterized by men, while women are only their bearers:
- hemophilia,
- blindness;
- syndrome Lesch - Naihan.
