Difference Between Linkage and Crossing Over

Main Difference

The main difference between linkage and crossing over is that linkage certifies genes in the same chromosome that are inherited together, whereas crossing over make sure the separation of genes and separate them into different gametes that are present in the same chromosome.

Linkage vs. Crossing Over

The distance present between two genes in the same chromosome is inversely proportional to the point of linkage, whereas the distance present between two genes in the same chromosome is directly proportional to the chance of crossing over. The role of linkage is to make sure that genes present on the same chromosome are inherited together at the same time and the same position; on the other hand, the role of crossing over is to make sure the separation of genes present on the same chromosome and to exchange genes between two homologous chromosomes.

In linkage, it makes sure the conservation of the parental traits into their offspring and next generations by inheriting them; on the contrary, in crossing over, it causes the various changes in the parental traits in their next generations and does not conserve the traits of their parents in their offspring. The main disadvantage for linkage is the age, which decreases the linkage with the increase of age; on the flip side, crossing over tends to increase with the increase of the age.

Linkage generally decreases the chance of variations in the next generation by inheriting same genes in generations by their parents so; it does not play a role in variation by keeping the same genes, while crossing plays an important role in variations in the next generation by inheriting different genes of the parents in their offspring.

Linkage tends to happen when two different genes are generally closer to each other in the same chromosome, whereas crossing over tends to happen when two different genes are usually present far apart from each other in the same chromosome. Additionally, the groups of genes are made in the linkage, whereas crossing over normally disrupts the gene groups by separating and exchanging them into different genres.

Linkage inherits the same genes while crossing over only happens during the process of prophase of meiosis 1. Linkage does not produce recombinant alleles; conversely, the crossing over generally tends to produce recombinant alleles.

Comparison Chart

LinkageCrossing Over
Linkage generally mentions the tendency of DNA sequencing to stay together in next-generation by inheriting the same genes.Crossing over generally refers to the exchange of segments of genes between two non-sister chromatids of homologous chromosomes, which results in non-identical chromatids.
Distance Between Two Genes
Inversely proportional to the point of linkageDirectly proportional to the happening of crossing over
Significance
To make sure that genes present on the same chromosome are inherited together at the same time and the same positionto make sure the separation of genes present on the same chromosome and to exchange genes between two homologous chromosomes
Maintenance of the Parental Traits
Makes sure the conservation of the parental traits into their offspring and next generations by inheriting themCauses the various changes in the parental traits in their next generations and do not conserve the traits of their parents in their offspring
Influence of the Age
Tends to decrease with the increase in ageIt tends to increase with the increase in age
Variations
Generally decreases the chance of variations in the next generation by inheriting the same genes in generations by their parents so, does not play a role in variation by keeping the same genesPlays an important role in variations in the next generation by inheriting different genes of the parents in their offspring
Occurrence
Happens when two different genes are generally closer to each other in the same chromosomeHappens when two different genes are usually present far apart from each other in the same chromosome
Gene Groups
The groups of genes are madeNormally disrupts the gene groups by separating and exchanging them into different genes
Happens
Inherits the same genesOnly happens during the process of prophase of meiosis 1
Recombinant Alleles
Does not produce recombinant allelesGenerally, it tends to produce recombinant alleles

What is a Linkage?

The term linkage has its broad means, which generally mentions the tendency of DNA sequencing to stay together in the next generation by inheriting the same genes. Linkage is the study of the inheritance of all genes which are present together in the specific chromosome. Linkage group, which generally equals the chromosome, is formed when genes are inherited together called linked genes from the parents in the specific chromosome.

The total number of linkage groups is generally equivalenting to its haploid number of chromosomes. The chromosome possesses several genes, and all of them are inherited together. Because of linkage, the genes are inherited together during the production of gametes present in the same chromosome.

Linkage generally occurs between genes that are located in very close vicinity to each other in the same chromosome, but genes that are present far apart from each other in the chromosome are partially linked, which means closer genes have greater strength than the genes which are present far away from each other. Linkage does not produce recombinant alleles.

So, the genes which are present far away can easily be separated during the recombination period. The genes which are present in different chromosomes normally cannot be linked, and independent assortment can be seen in these chromosomes in the dihybrid cross. A scientist T.H. Morgan done a series of experiments with the house fly (Drosophila) and proved that two genes are present in the chromosome pair in the coupling phase (cis) or repulsion phase (trans).

This whole phenomenon was called as linkage, and the genes were called linked genes. The linkage group numbers vary in every organism, such as the linkage group in man is 23 by matching to the number of chromosome n=23. Drosophila’s linkage group is 4.

What is Crossing Over?

The term crossing over can be understood by the concept that generally refers to the exchange of segments of genes between two non-sister chromatids of homologous chromosomes, which results in non-identical chromatids. So, crossing over can also be described as the tendency of genes which are present in the same chromosome to isolate and from each other into different gametes.

Therefore, crossing overplays a role to facilitates the genetic recombination to produce a new combination of alleles by exchanging their segments. Additionally, crossing over tends to happen at the synapse, which is the tight holding that usually keeps the two homologous chromosomes to each other. Crossing over only happens during the process of prophase of meiosis 1.

Crossing over has its main advantage in variations and the origin of new characters in the next generations, which also leads to genetic variations. But the flaw in crossing over is that it causes various changes in the parental traits in their next generations and do not conserve the traits of their parents in their offspring.

Key Differences

  1. Linkage causes the inheritance of genes that occurs together that are present on the same chromosome; on the other hand, crossing over causes the separation of genes that are present on the same chromosome.
  2. There is a reciprocal link between the distance and to the point of linkage generally present between two genes in the same chromosome, whereas there is a direct relationship between distance and to the chance of crossing over present between two genes in the same chromosome.
  3. Linkage makes sure the preservation of the parental characteristics into their offspring; on the contrary, crossing over generally does not preserve the characteristics of their parents in their offspring.
  4. With an increase in age, the linkage process decreases; on the flip side, with the increase of the age, crossing over process tends to increase.
  5. The chance of variations in the next generation is less in the linkage process by inheriting the same genes, while the chances of variations in the next generation are more in crossing over the process by inheriting the different genes.
  6. Linkage usually occurs when the distance between two different genes is very small in the same chromosome, whereas crossing over occurs when the distance between two different genes is very large in the same chromosome.
  7. Linkage produces groups of genes while crossing over normally disperse the groups of genes.
  8. Linkage transmits the same traits while crossing over occurs only during the prophase of meiosis 1.
  9. Linkage usually does not involve in the recombinant frequency; conversely, the crossing over generally involves in the recombinant frequency.

Conclusion

The above discussion concludes that the linkage certifies genes in the same chromosome that are inherited together and conserve the traits of the parents, whereas crossing over make sure the separation of genes and separate them into different gametes that are present in the homologous chromosomes and causes variations in genes in next generation.

Janet White

Janet White is a writer and blogger for Difference Wiki since 2015. She has a master's degree in science and medical journalism from Boston University. Apart from work, she enjoys exercising, reading, and spending time with her friends and family. Connect with her on Twitter @Janet__White

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