Linkage occurs when two different genes are located on the same chromosomes
- For this reason they are usually inherited together and end up in the same gamete
- Under normal circumstances, the linked genes on the same chromosome pass into the gamete and then into the offspring together
This is contrarty to Mendel's law of independent assortment.
If genes A & B had been on separate chromosomes, then there would have been more genetic variation in the gametes and in the offspring.
Independent assortment would have allowed parents AaBb to produce two types of games
- AB, Ab, aB, ab
Recombination occurs when alleles are exchanged between homologous chromosomes as a result of crossing over
Recombination allows Mendel's second law of independent assortment to operate and so increases the genetic varition in the gametes and hence in the offspring
The further apart two genes are on a chromosome, the more chance there is of crossing over occuring.
- This has been used to determine where a gene locus (position) is on a chromosome and so produce chromosome maps