The objective of this project is to determine if the apterous wing gene is linked with the given genes which is purple eye gene, black body gene, brown eye gene, sepia eye gene, spineless bristle gene and ebony body gene. Thus, a linkage map was constructed. Chi-Squared test was also done to determine these results were not occurring by chance. As a result, the apterous wing gene is linked to the purple eye gene, black body gene and brown eye gene. It is however not linked to the sepia eye gene, spineless body gene and ebony body gene.
Genetic mapping is a method used to determine the location of genes on the chromosome and distance between the genes with the aid of a linkage map. Genetic mapping is done to research gene locus due to the crossing over of the non-sister chromatids in meiosis. The sister chromatids will separate from each other and then later joined back resulting in exchange of chromatids. Thus, exchange of genes occurs (Saraswathy & Ramalingam 2012).
In genetics, markers will be present in the linkage map. They are used as gene tags to identify the gene of interest. Example of markers are PCR-based markers and DNA sequence-based markers (Shabir et al., 2017).
To construct genetic map, the parents of a desired species must have phenotypes which are different from each other. The, test cross must be done between the parents to produce a F1 progeny. The F1 progeny is then allowed to self-cross to produce F2 progeny. After that, data of the F2 progeny is collected to calculate the recombinant frequencies and thus construct a genetic map.
To determine the location of the genes, the recombinant frequencies which is the number of recombinants to the total number of progenies need to be calculated. The phenotype of progeny must also be recorded down. The value calculated is the distance between the genes in the chromosome. Centimorgan is the general unit used in genetics. One percent of recombination frequency equals to one centimorgan (Friedmann, Dunlap & Goodwin 2016).
By observing the location and distance of the genes on the chromosome, if two genes in the same chromosome are located close to each other, this means that the two genes are linked and will be inherited together in crossing over. Likewise, if the two genes on the chromosome are located far from each other, the two genes are partially-linked and will separate from each other in cell division. Also, if the two genes are not even on the same chromosome, they are termed unlinked (Saraswathy & Ramalingam 2012). Thus, the lower the recombinant frequency means the lower chance of crossing over which results in occurrence of smaller proportion of recombinant progenies.
Genetic mapping is useful in many applications such as determining the genes that caused hereditary diseases. It is also used for determining the gens that is responsible for producing the traits in animals and plants.