Topic: Linkage is an exception to the Law of Independent Assortment.
Key Points
Law of Independent Assortment
Proposed by Gregor Mendel.
States that the alleles of two (or more) different genes get sorted into gametes independently of one another.
The allele a gamete receives for one gene does not influence the allele received for another gene.
Linkage
An exception to the Law of Independent Assortment.
Occurs when two genes are located on the same chromosome.
These genes tend to be inherited together because they are physically connected.
Reduces the genetic variation in offspring relative to independent assortment.
Details
Linked Genes
Genes that are close together on a chromosome are said to be linked.
The closer the genes are, the less likely they are to be separated during recombination.
Genetic Recombination
During meiosis, crossing over can occur, and linked genes can be separated.
However, recombination is less frequent between closely linked genes.
Implications
Linkage affects the expected ratios of phenotypes in offspring.
Important for understanding genetic inheritance patterns and mapping genomes.
Examples
Certain traits in organisms that are commonly inherited together are often linked genes.
The classic example includes Morgan's work with fruit flies, linking traits like body color and wing shape.
Conclusion
While the Law of Independent Assortment is a foundational principle in genetics, linkage provides a critical exception that enhances our understanding of genetic inheritance.
Understanding linkage is crucial for fields such as genetic counseling, evolutionary biology, and genomics.