7. GENETIC MAPS IN FRUIT TREE SPECIES

Question 1

What are the basis of genetic mapping?

Answer 1

1. Genetic mapping is based on the principle that genes (markers or loci) segregate via chromosome recombination during meiosis (i.e. sexual reproduction), thus allowing their analysis in the progeny (Paterson, 1996).
2. During meiosis, chromosomes assort randomly into gametes, such that the segregation of alleles of one genes independent of alleles of another gene. This is stated in Mendel’s second law and is known as the law of independent assortment.
3. The law of independent assortment always holds true for genes that are located on different chromosomes, but it does not always hold true for genes that are on the same chromosome.
4. When two genes are close together on the same chromosome, they do not assort independently and are said to be linked. Genes that are closer together or tightly-linked will be transmitted together from parent to progeny more frequently than those genes located far apart.