This particular species of fly was taken because of its characteristics, since it has a low number of chromosomes, easily recognizable phenotypic variability and whose chromosomal location is known, as well as easy growth in simple culture media, which facilitated the experiment. and determine the pigments responsible for the coloration of eyes and body from a thin layer chromatography.

We take 4 filter papers of 23 cm wide by 28 cm high, in the line of application we sow the heads and the bodies each one in different points, as it is described next with the symbols used in the laboratory guide to name the mutations:

Paper # 1. Fly heads: + ♀ w♀ ♀we ♀wa ♀wa / w ♀ we / wa.

Paper # 2. Bodies of fly heads placed on paper # 1.

Paper # 3. Fly heads: + ♀ w♀ ♂w ♀Cu ♀bw ♀Cu / bw.

Paper # 4: body of the fly heads placed on paper # 3.

After the planting we placed the papers in the buckets containing the solvent system 20: 3: 7 butyl alcohol / glacial cetico acid / distilled water. Once the chromatography run was developed, the papers were visualized, using a UV light viewer.

In specimens of wild D. melanogaster, the pigmentation of the eyes is due to the presence of two types of pigments: pteridins and ommochromes; the former are brightly colored compounds that fluoresce and emit a characteristic color light when viewed under UV light. The ommochromes are brown and do not fluoresce in UV light. The production of each type of pigment involves a sequence of known biosynthetic steps. The precursor of the pteridines is 2-amino-4-hydroxypteridine, while that of ommochromes is the amino acid tryptophan. Once formed these pigments must be fixed on the protein granules of the ommatidia that make up the facets of the eyes. The set of these pigments in wild individuals makes the eyes are red. In the fixation of the pigments, the activity of another gene independent of those genes related to biosynthesis intervenes. It is the wild allele "white", the activity of the gene involved in the process of fixing the pigments to the granules of ommatidium protein. Thus, the w / w mutant females and the hemigo w / Y males are unable to fix ocular pigments, and although they can biosynthesize them, their eyes are white. This result is reflected in the chromatograms performed (figure 5). A mutant strain in a determined metabolic sequence, as is the case of the formation of pigments, can be recognized because it lacks the final product of the biosynthetic sequence, however, it presents the compound that precedes the mutated biosynthetic step in the sequence.

By chromatography on paper and using a system of suitable organic solvents, it was possible to separate the pigments into different identifiable spots. For a strain of wild flies, chromatography allows the separation of 7 different pteridines: drosopterin, golden yellow; isoxantopterin, purple; sepiapterin, lemon yellow; 2-amino-4-hydroxypterin, blue in color; biopterin, violet blue; xantopterina, blue-green color and isosepiapterina, orange yellow. The eye-color mutants of D. melanogaster present a pteridin pattern different from the pattern of the wild strain. To discern phenomena of allelic interaction, it is very important to establish the level of observation of the individuals under study, and thus be able to establish the relationship of dominance between a gene and its allele. In the case of homologous individuals (AA or aa), the joint expression of both identical alleles leads to the expression of a characteristic, dominant or recessive phenotype. The heterozygous Aa individuals may be phenotypically identical to the dominant AA homociples, however, when the phenotypic analysis is performed at another level of observation, for example at the biochemical level, the phenotype differences between individuals AA and Aa can be established. . The level of observation of a heterozygous individual may reveal the activity or absence of activity of a recessive gene. An analysis of the products synthesized by the genes in question, will allow to recognize the activity or hidden inactivity of the recessive allelic gene that is masked by the presence of the product of the dominant gene in the heterozygote, this will allow to establish differences between homologous and heterozygous individuals.