Linkage, crossing over and chromosomal mapping
Linkage :- When two alleles present together on a chromosome are inherited together, it is called linkage. Note:- Crossing over can be up to 50% only. Linkage groups:- A linkage group is a linearly arranged group of linked genes which are normally inherited together except for crossing over. Types of linkage:- i. Complete linkage:- > The genes located on the same chromosome do not separate and are inherited together over the generations due to the absence of crossing over. > Complete linkage allows the combination of parental traits to be inherited as such. > It is rare but has been reported in male Drosophila and some other heterogametic organisms. ii. Incomplete linkage:- > Genes present in the same chromosome have a tendency to separate due to crossing over and hence produce recombinant progeny besides the parental type. > The number of recombinant individuals is usually less than the number expected in independent assortment. ...