Currently, many patterns of inheritance of the properties (traits) of organisms have been established. All of them are reflected in the chromosome theory of inheritance of the traits of an organism. We name the main points of this theory.
• Genes, being carriers of the hereditary properties of organisms, are units of hereditary information.
• The cytological basis of the genes are groups of adjacent nucleotides in the DNA chains.
• Genes located in the chromosomes of the nucleus and cells are inherited as separate independent units.
• In all organisms of the same species, each gene is always located in the same place (locus) of a particular chromosome.
• Any changes in the gene lead to the appearance of its new varieties – alleles of this gene and, consequently, to a change in the trait.
• All chromosomes and genes in an individual are always present in its cells in the form of a pair that enters the zygote from both parents during fertilization.
• Each gamete can have only one identical (homologous) chromosome and one gene from an allelic pair.
• During meiosis, various pairs of chromosomes are distributed between gametes independently of each other and quite by chance the genes located on these chromosomes are also inherited.
• Crossing is an important source of new gene combinations.
• The development of organisms occurs under the control of genes in close interconnection with environmental factors.
• Identified patterns of inheritance of properties are observed in all, without exception, living organisms with sexual reproduction.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.