Chromosomal theory of heredity
Based on the experiments carried out, T. Morgan formulated the law of linked inheritance.
Genes located on the same chromosome are inherited together, forming a linkage group, and the strength of linkage between them is inversely proportional to the distance between these genes.
This law was used as the basis for the chromosomal theory of heredity.
Each gene has a specific locus on the chromosome.
The genes on the chromosome are arranged linearly in a specific sequence.
The genes of one chromosome are linked, therefore they are inherited mainly together.
The frequency of crossing over between genes is equal to the distance between them.
Genetic maps of chromosomes
A genetic map is a diagram of the mutual arrangement and relative distances between genes of certain chromosomes that are in the same linkage group.
It is a segment of a straight line on which the order of the genes is plotted and the distance between them in morganids is indicated.
Genetic chromosome maps are compiled for many types of organisms: insects (fruit fly, mosquito, cockroach, etc.), fungi (yeast, aspergillus), for bacteria and viruses.
Human genetic maps are used in medicine to diagnose a number of severe hereditary diseases.