Linkage and crossing over are two related, yet different phenomena occurring in eukaryotic organisms. Genetic linkage or, simply, the linkage is the tendency of genes to stay together in a chromosome while crossing over is a phenomenon through which genetic information is exchanged in the germline. Both of these play an important role in heredity. Both the events are somewhat related to each other. However, Linkage is more about the tendency of genes in a chromosome to inherit together. Through crossing over, the genes separate and segregate into different gametes.
We will learn more about genetic linkage and crossing over and the differences between them in this article.
As explained above, genetic linkage means the tendency of the genes or DNA sequences on a chromosome to be inherited together during meiosis of sexual reproduction. Linked genes are the ones located on the same chromosome. For example, genes on hair colour and eye colour. That is why some individuals inherit hair and eye colours together. Such as black hair with brown eyes or individuals with brown hair and blue eyes inherited from parents.
The exchange of chromosomes between non-sister chromatids to form gametes is crossing over. Crossing over shuffles the alleles on parental chromosomes, so that the gametes carry the combination of genes from mother and father. In simple language, it is the swapping of genetic material in the germline. During meiosis, or formation of an egg cell and sperm cells, paired chromosomes get aligned so that similar DNA sequences from the paired chromosomes come against one another. This phenomenon accounts for genetic variation in sexually reproducing organisms and it is also essential for normal segregation of chromosomes.
The Difference Between Linkage and Crossing Over
Crossing over is the process of separation of genes between homologous pairs into various gametes. Linkage is the tendency of inheriting genes together on the same chromosome.
Linkage occurs when two genes are closer to each other on the same chromosome. On the other hand, crossing over takes place when two genes are located far apart on the same chromosome.
Crossing over may disrupt the gene groups made by linkage.
Unlike the linkage, crossing over only occurs during the prophase of meiosis I and it produces recombinant alleles, which is not the case in the linkage.