Question

In garden peas, tall plants (T) are dominant to short plants (t), and round pods (R) are dominant to constricted pods (r). A true breeding, homozygous tall plant with round pods (TTRR) was crossed with a true-breeding short plant with constricted pods (ttrr). All F1 plants were tall with round pods (TtRr). When the F1 plants were crossed, the F2 generation contain 75 tall/round and 25 short/constricted plants. What can you conclude about the chromosomal location(s) of these genes

Answer 1

Answer:

Based on the given information, the study of different varieties of the garden pea was done, that is, tall plants with round pods having homozygous genotype TTRR, and the short plants with constricted pods having homozygous genotype ttrr. Post crossing the mentioned varieties of garden pea, the F1 generation comprises tall plants with round pods having the genotype TtRr. While when the crossing of F1 generation plants was done, the plants obtained in the F2 generation demonstrated the phenotype, that is, tall plants with round pods, which is 75 in number and short plants with constricted pods, which is 24 in number.  

This shows that the genes would have been the linked genes, as they would have been situated very close together on the homologous chromosomes, and because of this linkage, the expression of the genes would have taken together.  

In case, if there was no linkage, then the genes would have assorted independently, and the offspring produced in the F2 generation would have shown the phenotypic ratio with the features of tall plants with round pods (9), short plants with round pods (3), tall plants with constricted pods (3), and short plants with constricted pods (1).  

Though the above-mentioned situation did not occur and the plants obtained in the F2 generation demonstrated the phenotype, that is, tall plants with round pods, which is 75 in number and short plants with constricted pods, which is 24 in number. This further puts more emphasis on the fact that the genes for both the phenotypes were linked due to which expression of only the mentioned two varieties took place and the other two failed to do so.