A chromosome possesses many genes & all genes present in the chromosome are inherited together.
Linkage: Study of inheritance of all genes present in a chromosome together.
- All genes in a chromosome are together referred as linked genes & they form a linkage group.
- The total number of linkage group in an organism is equal to its haploid number of chromosomes.
Bateson & Punnet:
- While working on sweet pea (Lathyrus odoratus) observed that genes for flower color & pollen shape remain together and do not assort independently according to Mendel’s law of Independent assortment.
- Test cross failed to produce 1:1:1:1 ratio & instead produced 7:1:1:7.
- They gave the Coupling & Repulsion theory:
- Coupling: when genes come from the same parent they enter the same gamete & are inherited together.
- Repulsion: genes are inherited separately when genes come from different parents & they enter different gametes