Type of Linkage

There are two main types of linkage: complete linkage and incomplete linkage.

1. Complete Linkage: (See above Figure)

   • Complete linkage occurs when two genes are located very close together on the same chromosome. In this case, they are so close that they are almost always inherited together as a single unit, without undergoing crossing over between them during meiosis.

   • This means that the alleles of these genes tend to stay together and are rarely separated by recombination events.

   • Complete linkage can lead to the inheritance of specific combinations of alleles (called haplotypes) in a predictable manner.

2. Incomplete Linkage: (See above Figure)

   • Incomplete linkage (also known as partial linkage) occurs when two genes are located near each other on the same chromosome but are not close enough to always be inherited together.

   • During meiosis, there is a possibility of crossing over between these genes, leading to the exchange of alleles between homologous chromosomes.

   • As a result, alleles from these genes can be inherited independently of each other in some offspring, breaking the linkage between them.

   • The degree of linkage between two genes can be quantified by the recombination frequency, which measures how often crossing over occurs between them. Lower recombination frequencies indicate stronger linkage, while higher frequencies indicate weaker linkage.

"Now here comes a critical question, "how to determine which two genes are close to each other and which are further apart on a chromosome? " and for this, one must have to analyze their Recombination Frequency. 

Here comes the concept of genetic mapping or linkage mapping." 

Click here to understand "How to calculate Recombination Frequency?" 🆗