Principles of Inheritance and Variations — BIOLOGY STD 12 Science — Question

(a) Linkage : "The genes which are located on the same chromosomes are linked together and pass together from generation to generation while those on other chromosomes are freely assorted."
(b) Linkage Groups : A set of genes at different loci on the same chromosome that except for crossing over tend to act as a single pair of genes in meiosis instead of undergoing independent assortment.
(c) Complete (or absolute) Linkage : It is defined as the state in which two loci are so close together that alleles of these loci are virtually never separated by crossing over. The closer the physical location of two genes on the DNA, the less they are to be separated by a crossing over event.
(d) Incomplete Linkage : It produces new combinations of the genes in the progeny due to the formation of chiasma or crossing over in between the linked genes present on homologous chromosomes.