Page 11 - Lesson Notes- Principle of inheritance & Variation

Chromosomal Theory of Inheritance

Chromosome as well as gene both occurs in pair. The two alleles of a gene pair are
located on the same locus on homologous chromosomes.

Sutton and Boveri argued that the pairing and separation of a pair of chromosomes

would lead to segregation of a pair of factors (gene) they carried.
Sutton united the knowledge of chromosomal segregation with mendelian principles

and called it the chromosomal theory of inheritance.

Linkage and Recombination

When two genes in a Dihybrid cross were situated on same chromosome, the
proportion of parental gene combination was much higher than the non-parental type.

Morgan attributed this due to the physical association or the linkage of the two genes
and coined the linkage to describe the physical association of genes on same

chromosome.

The generation of non-parental gene combination during Dihybrid cross is called
recombination. When genes are located on same chromosome, they are tightly linked

and show very low recombination.

Difference between crossing over and linkage

Crossing over Linkage

1. It leads to separation of linked genes 1. keeps the genes together

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