One of the most important properties of any living organism is heredity underlying evolutionary processes of the planet, as well as the conservation of species diversity on it.The smallest unit of heredity gene acts - a structural element of the DNA molecule responsible for transmitting genetic information associated with a particular feature of the body.Depending on the degree of stand dominant and recessive genes.A characteristic feature of the dominant unit is the ability to "suppress" recessive, exerting a decisive influence on the organism, not allowing them to appear in the first generation.However, it is worth noting that, along with a complete domination observed incomplete, in which the dominant gene is not able to completely suppress the expression of the recessive and superdominance providing relevant manifestation of symptoms in the form of stronger than homozygous organisms.Depending on which allele (i.e., which are responsible for the development of the same sign) genes it receives from parent animals heterozygous and homozygous allocated organisms.
Determination homozygous organism
Homozygous organisms - are objects of nature, with two of the same (dominant or recessive) gene on a particular basis.A distinctive feature of the next generation of homozygous individuals is a lack of segregation of characters and their monotony.This is explained mainly by the fact that a genotype homozygous organism contains only one type of gamete, designated by a capital letter when it comes to dominant and recessive at the mention of line.Heterozygous organisms are characterized in that they contain different allelic genes, and, accordingly, constitute two distinct types of gametes.Homozygous organisms by major recessive alleles, can be described as aa, bb, aabb etc.Accordingly, homozygous organisms dominant alleles are code AA, BB, AABB.
patterns of inheritance
Crossing two heterozygous organisms genotypes which can be roughly described as Aa (where A - the dominant, and - a recessive gene), provides the opportunity to receive an equal probability of four different combinations of gametes (variant genotype) withcleavage of 3: 1 phenotype.Under genotype in this case means a series of genes that contain a diploid set of a particular cell;under the phenotype - the system of external and internal features of the organism in question.
dihybrid cross and its features
Consider patterns associated with mating process, which involved homozygous organisms.In that case, if there is a two-hybrid or poligibridnoe crossing, regardless of the nature inherited attributes, the cleavage occurs at a ratio of 3: 1, where the law is valid for any number of them.Crossing individuals of second generation in this case forms the four main types of phenotypes in a ratio of 9: 3: 3: 1.It is worth noting that the law is fair for homologous pairs of chromosomes, gene interactions within which is not carried out.
