An experiment of Bateson and Punnet:
- Bateson and Punnet (1906) did a dihybrid cross on plants of blue flowers and long pollens with red flower and round pollen plant and found the following results.
[Abbreviations: Blue flower = B, Red flower = b, Long pollens = L and round pollens = L.]
- A cross between Blue flower and long pollens (BBLL), and red flower and round pollens yielded blue flowers and long pollens in the F1 generation.
Now they made a test cross between heterozygous F1 offsprings (B bLl) with homozygous recessive parent (bbll). By the concept of linked genes and independent assortment BbLl should give four kinds of gametes and hence four phenotypes in equal proportions 1:1:1:1 were expected.
But Bateson and Punnet obtained the following results –
- The above results in 7:1:1:7 ratio were obtained. This suggests that new combinations or recombinants were less and a number of parental plants were more.
- It means the selected genes for the study have not followed the law of independent assortment, but their nature showed linked inheritance or they show Linkage.
- The genes present on the same chromosome show their nature to inherit together are called Linked genes and the incidence is known as Linkage.
- Sometimes a group of genes found on a single chromosome are inherited together, is called Linkage group.
