Depending on absence or presence of recombinant phenotype:
a) 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.
b) 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
Depending on whether all or some dominant and some recessive genes are linked together:
i) Coupling phase of linkage: Dominant alleles of the linked genes are present in the same chromosome. Eg: Colored full/ color less sunken genes in maize.
ii) Repulsive phase of linkage: Dominant alleles of some genes and recessive alleles of other gene are present in the same chromosome. Eg: Colored shrunken/ color less full genes in maize.
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