•  The inheritance of the chromosomes is always as intact units where the linked alleles of paired genes will be inherited together because they are on the same chromosome.

•   If a pair of gene is inherited independently then it is expected that either the genes are on different chromosomes or not linked although in same chromosome which is why they are sometimes inherited together and sometime separately due to crossing over.

Genes (markers or loci) segregate via chromosome recombination during meiosis (i.e. sexual reproduction), thus allowing their analysis in the progeny. Chromosomes assort randomly into its gametes under meiotic cell division and these alleles segregate independently (according to Mendel's law of independent assortment).When two genes are close together on the same chromosome and they do not assort independently, they are said to be linked. At the beginning of meiosis, a homologous chromosome pair may intertwine and exchange sections of chromosome. Such process or set of processes is called recombination (also called cross-over or strand exchange). It results in two types of gametes:

i)  No crossing-over → parental gametes

ii)  Crossing over → recombinant gametes

Genes that are located on different chromosomes assort independently (unlinked) and have a recombination frequency of 50%. However, linked genes have recombination frequency of less than 50%.

Importance of Genetic of Mapping

To develop appropriate mapping population and decide the sample size.

►Selecting the type of molecular marker(s) to genotype the mapping population

►Screening of parents for marker polymorphism followed by genotyping the mapping population (parents and all progenies).

►To perform the linkage analyses (i.e. calculating pair wise recombination frequencies between the markers, establishing linkage groups, estimating map distances, and determining map order) via statistical programs.