Question

Who proposed the chromosomal theory of linkage?
A. Morgan
B. Castle
C. Both A and B
D. Bateson

Answer 1

Hint: Linkage is the tendency of the genes present in the same chromosome to stay together in hereditary transmission.

Complete answer: The principle of linkage was put forward as a regular concept by Morgan on the fruit fly (Drosophila melanogaster) as they could be grown in a simple synthetic medium in the laboratory, complete life cycle in two weeks, in a single mating produce large progeny and clear differentiation of sex can be seen.
Postulates of the chromosomal theory were formulated by Morgan and Castle. The postulates were –
1. Genes lie in a linear order in the chromosome.
2. The genes show linkage i.e. stays together in hereditary transmission are located on the same chromosome.
3. Genes tend to stay in parental combinations other than occasional crossing over.
4. The distance between the linked genes in the chromosome determines the strength of linkage. The closer the genes are located, the stronger the linkage.

Additional information: There are two types of linkage
1. Complete linkage
2. Incomplete linkage
Complete linkage: The genes are closely located in the chromosome as a result complete linkage of the chromosome takes place.
Incomplete linkage: the genes are located distantly from the chromosome as a result in the complete linkage of the chromosome takes place

So the correct answer is option is C. Both A and B.

Note: The principle of linkage was first discovered by Bateson and Punnet by using Sweet Pea but the chromosomal theory was formulated by Morgan and Castle by using the fruit fly (Drosophila melanogaster).