Question

Mendel was not able to say anything about recombination and crossing over because
A) He did not have a large strong microscope.
B) He chose only pure gametes.
C) Traits he selected were not linked and present on different chromosomes or were far apart.
D) Traits he chose had no genes.

Answer 1

Mendel considered that factors (now called genes) are responsible for inheritance of a character from one generation to another and these characters have alternative forms called alleles located on chromosomes.

Complete answer:
Mendel chose 7 contrasting characters in the pea plant and crossbred them to study about the inheritance of characters. He performed both monohybrid and dihybrid cross in which the parents were distinguished on the basis of difference in one and two characters respectively. After a detailed study, he proposed 3 laws of inheritance-
Law of dominance- characters occur in contrasting allelic forms. Among these contrasting alleles one is dominant and other is recessive.
Law of segregation- each pair of alleles separate or segregate into gametes in sexual reproduction. These gametes, one from male and another from female fuse to form zygote that ultimately gives rise to a complete offspring.
Law of independent assortment – when he performed dihybrid cross, he analyzed that segregation and passing on of one character is independent to that of another character.
There are some phenomenons that cannot be explained using Mendelian genetics like recombination and crossing over. In recombination and crossing over, the piece of DNA in a chromosome is broken and joined to the part of another homologous chromosome pair up during prophase 1 of meiosis. This results in an increase in variations and diversity in an organism.
In case of linkage two or more genes are linked together i.e. they are located so close to each other that they are inherited together for several generations. Mendel was unable to explain anything about recombination and crossing over because the characters he chose for the study were either located on different chromosomes or far apart on the same chromosome. The characters were not linked to each other and hence Mendel did not observe recombination and crossing over in the 7 contrasting characters he studied.

Hence, the correct answer for this question is C, i.e. Traits he selected were not linked and present on different chromosomes or were far apart.

Note: If any 2 or more of the 7 contrasting traits would have been linked, then there is a possibility that Mendel would have observed recombination and crossing over.