Gene Mapping Report: Exploring Significance and Recent Improvements

This report provides an overview of gene mapping, starting with its historical context and significance. It explains how gene mapping, initially illustrated by Thomas Hunt Morgan, represents recombination frequencies and distances between markers. The report highlights the importance of gene maps in linking traits to genetic regions, improving animal breeds and crops, and understanding species diversification. It also covers applications in medicine, microbial genetics, and positional cloning. The report further discusses improvements in gene mapping techniques, including the use of functional mapping models and the investigation of inherited haplotypes. The report concludes by emphasizing the importance of gene mapping techniques for determining mutations and mapping recombination frequencies between different markers.

Running head: GENE MAPPING – SIGNIFICANCE AND IMPROVEMENTS
Gene mapping- significance and improvements
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1GENE MAPPING – SIGNIFICANCE AND IMPROVEMENTS
The technique of gene mapping was first illustrated by Thomas Hunt Morgan in 1911
while studying the genetics of Drosophila. Gene mapping or linkage mapping refers to a
representation of recombination frequencies and relative distance between markers loci in
homologous chromosomes (Robinson 2013).
Significance- Gene maps are essential for providing an avenue to link a trait of particular
interest to a specific genetic region in the chromosome. Genetic mapping helps in utilizing a
mechanism that tracks the co-segregation of different genetic markers associated with particular
traits in a population. Such markers can be utilized in agriculture to improve animal breeds and
resistant crops (Morrell, Buckler and Ross-Ibarra 2012). They are used in evolutionary studies to
understand the mechanism of diversification of different species. Comparative mapping between
or within taxa helps in revealing regions where there is gene order conservation. They locate
regions of chromosomal duplication. These maps have huge significance in medicine and help in
identification of people who are vulnerable to a host of genetic diseases. They detects carrier in
recessive disorders where the affected gene is not directly expressed (Eyre et al. 2012). Microbial
genetic maps help in producing energy by harnessing the power of bacteria and also help
researchers to develop environment friendly products. Positional cloning is another application.
It has been utilized in isolating maize genes in recent years. Genetic mapping also determines the
effect of location on the expression of genes and identifies several factors that affect
recombination between genes. These maps also recognize the non-functional pseudogenes and
their probable role.
Eye pigments- The eye colour pigments in Drosophila are produced by two distinct
biochemical pathways: the pteridine pathway (pale blue to yellow to scarlet pigment) and the
ommochrome pathway (brown pigment). A large number of genes are associated with the eye

2GENE MAPPING – SIGNIFICANCE AND IMPROVEMENTS
colour phenotype. Wild type eye color in Drosophila is red. Several studies have shown the
brown pigment to be xanthommatin, which is a member of the ommochrome class, called
ommatins. A homozygous recessive mutation in the pteridine pathway that produces the pigment
drosopterin will prevent the production of the bright red pignment and results in a dull brown
colour (Grant et al. 2016). If there occurs a loss-of-function mutation in the cinnabar gene,
responsible for synthesis of brown pigment, the phenotype will be bright red for such
homozygous cinnabar mutant flies.
Improvements- The original gene mapping approaches were based on single point
variations and they failed to detect the developmental changes in traits. Investigation of inherited
haplotypes will prove effective in locating the human gene map. However, these haplotypes can
fail in incomplete disease penetranceor etiologic heterogeneity (Sun and Wu 2015). Therefore, a
functional mapping model (computer programs like MENDEL, VITESSE and LINKAGE) that
focuses on statistical framework can be used, which will focus on estimation of the loci related to
the disease based on the markers and phenotypes.
Thus, it can be concluded that gene mapping techniques are essential for mapping the
recombination frequencies between different markers on homologous chromosomes. They are
widely used to determine the mutations that occur during meiotic recombination in Drosophila.

3GENE MAPPING – SIGNIFICANCE AND IMPROVEMENTS
References
Eyre, S., Bowes, J., Diogo, D., Lee, A., Barton, A., Martin, P., Zhernakova, A., Stahl, E., Viatte,
S., McAllister, K. and Amos, C.I., 2012. High-density genetic mapping identifies new
susceptibility loci for rheumatoid arthritis. Nature genetics, 44(12), pp.1336-1340.
Grant, P., Maga, T., Loshakov, A., Singhal, R., Wali, A., Nwankwo, J., Baron, K. and Johnson,
D., 2016. An eye on trafficking genes: Identification of four eye color mutations in
Drosophila. G3: Genes, Genomes, Genetics, 6(10), pp.3185-3196.
Morrell, P.L., Buckler, E.S. and Ross-Ibarra, J., 2012. Crop genomics: advances and
applications. Nature reviews. Genetics, 13(2), p.85.
Robinson, R., 2013. Gene mapping in laboratory mammals. Springer.
Sun, L. and Wu, R., 2015. Mapping complex traits as a dynamic system. Physics of life
reviews, 13, pp.155-185.