Linkage in Sweet Pea

Linkage in sweet pea (Lathyrus odoratus) refers to the phenomenon of certain genes located on the same chromosome being inherited together more frequently than expected by independent assortment. Sweet pea, like many other organisms, exhibits genetic linkage, and this phenomenon was first studied in sweet peas by British geneticist William Bateson and American geneticist Edith Rebecca Saunders.

Key points related to linkage in sweet pea:

1. Gene Pairs on Chromosomes: In sweet pea, as in many other organisms, genes are located on pairs of homologous chromosomes. Each gene pair consists of two alleles, one inherited from each parent.

2. Observation of Linkage: Bateson and Saunders conducted experiments with sweet peas to study the inheritance of various traits. They noticed that certain traits seemed to be inherited together more often than expected based on Mendel’s principle of independent assortment.

3. Discovery of Linkage Groups: Based on their observations, Bateson and Saunders proposed the concept of “linkage groups.” Linkage groups are sets of genes located on the same chromosome that tend to be inherited together because they are physically close to each other on the chromosome.

4. Recombination and Crossing Over: The phenomenon of genetic linkage is due to the physical proximity of genes on the same chromosome. However, it’s important to note that genetic recombination can still occur during meiosis. This occurs through a process called crossing over, where homologous chromosomes exchange segments. Crossing over can break the linkage between genes within a linkage group.

5. Map Units: To quantify the degree of linkage between genes, scientists introduced the concept of map units (also known as centimorgans). One map unit represents a 1% chance of crossing over occurring between two linked genes during meiosis. By measuring the frequency of recombination, geneticists can estimate the distance between genes on a chromosome in map units.