When are gene loci said to be linked?

Sourav PanNovember 9, 2024

Answered

Gene loci are said to be linked when they are located close together on the same chromosome. This proximity affects how these genes assort during meiosis, particularly during the formation of gametes.

Key Points about Linked Genes

1. Proximity on Chromosomes: Linked genes are physically close to each other on a chromosome, which means that they tend to be inherited together more frequently than genes that are far apart or located on different chromosomes. This is due to the reduced likelihood of recombination (crossing over) occurring between them during meiosis.
2. Deviation from Independent Assortment: According to Mendel’s law of independent assortment, alleles of different genes segregate independently of one another. However, when genes are linked, they do not assort independently. Instead, the alleles for linked genes tend to be inherited as a unit because they are less likely to be separated by recombination events during meiosis .
3. Recombination Frequency: The degree of linkage can be quantified by calculating the recombination frequency between two loci. A lower recombination frequency indicates that the genes are closely linked, while a higher frequency suggests that the genes are further apart or unlinked .
4. Linkage Maps: Geneticists can create linkage maps based on recombination frequencies, which illustrate the relative positions of genes on a chromosome. These maps help in understanding gene order and distances between loci .
5. Examples in Genetics: In practical terms, if two genes are located very close together on the same chromosome (for example, gene A and gene B), offspring produced from crosses involving these genes will show a higher proportion of parental combinations (AB and ab) compared to recombinant combinations (Ab and aB). This observation is indicative of genetic linkage