Question

Mendel could not find recombination and crossing over because
(a)Traits he chose were either present on different chromosomes or were far apart
(b)Traits chosen by him were not influenced by genes
(c)He did not have a high power microscope
(d)He selected only pure types

Answer 1

Recombination is the process of production of a new combination of traits as opposed to the parental combinations due to the process of crossing over that takes place during the pachytene stage of prophase-I in meiosis.

Complete answer:
Mendel chose 7 pairs of contrasting characters and they were present quite far from each other on the chromosomes. Due to this distance, there was no recombination between the traits as the effects of crossing over are prominent when the genes are present closely next to each other. Due to the genes being present on different chromosomes, independent assortments of characters took place leading to the expected parental and recombinant phenotypes.

Additional Information:
Let us know more about recombination and crossing over.
-Linkage was discovered when Morgan was performing a dihybrid cross in Drosophila, but the dihybrid ratio was not the same as Mendel’s.
-He noticed that the genes present on the same chromosome or very near did not show recombination and were tightly linked to each other.
-Closer the genes were present, the higher was the linkage seen in between them.
-Due to the linkage between two genes, the ratio of dihybrid cross will have a high ratio of parental combinations than that of non-parental or recombinant combinations.
So, the correct option is ‘Traits he chose were either present on different chromosomes or were far apart’.

Note: -Morgan was studying the inheritance of sex-linked genes in Drosophila.
-Using the frequency of recombination as a measure of the distance between the gene pairs, Alfred Sturtevant mapped the position of genes on the chromosomes.
-The unit used for the distance between two genes on a chromosome is centiMorgan (cM).