Drosophila melanogaster is a model organism used in genetics and various research in cellular and molecular biology for many years. This organism is known for its short life cycle, small size, genetic variability, and its in-expensive trait to be studied in the laboratories. Thomas Morgan, an American geneticist is heavily credited for his work in discovering eye pigment mutation in the flies. He discovered mutation of white eyed Drosophila and concluded they were sex-linked. For many years, 75% specific genes in Drosophila have equivalency with humans in relation to certain diseases. Disease include cancer, renal disorders, Parkinson’s disease, and Azhelmer’s. (Russel and Tikko 2002).
The recessive allele rugose (rg) is one of many genes studied for eye color pigmentation in D. melanogaster. rugose was first seen as a rough eye phenotype due to abnormal retina and cone development. This abnormality resulted in loss of cone cells. Furthermore, this gene encodes for a kinase protein A and is mandatory for retinal formation and cell differentiation. The gene rugose (rg) is an aging gene, that plays a role in physiological age and senescence. Fecundity changes are also incorporated into this, and assimilate dramatically with age. SNPs, otherwise known as single-nucleotide polymorphisms, affect fecundity and life span as well. With this said, increase in SNP levels, result when comparing fecundity with age. This relation provides adequate support and provides theory of aging (Durham, 2014).
At the biological level rugose participates in imaging circadian pacemakers in order to detect brain study and intact cAMP levels by a neuropeptide pigment dispersing factor also known as PDF. In some flies, pacemakers were elevated by, activating ortholog of mammalian adenylate cyclase 3 (AC3), however it seemed to have no effect. Although, a different isoform was utilized known as AC78C by RNAi which reduced, but did not completely take usage of PDF (Duvall, 2013).
Phenotypic characteristics in the mutation of the gene
The sex-linked recessive rugose (rg) gene is located on chromosome 1 is observed to have small rough eye phenotype showing an abnormality in the ocelli. Many are seen with two or three cone cells in their ommatidia when normal complements are observed to have four. In comparison to wild type the ommatidia are not hexagonal in shape. rugose (rg) bristles are positioned irregularly and excess bristles tend to form at the corner of the ommatidia. Photo receptors are also lacking in the ommatidia and position of them tend to be disoriented resulting in disformity in the retina. Wings are curled upward, thin and frayed toward the margins with body being pale in color (lindsley,1992). These phenotypic classes cause a mutation in both dominant and recessive alleles and contribute in being lethal. Two alleles in particular address this chromosomal effect; rugose (rg1) and rugose (rg7) to signify differences as rugose (rg) in the phenotype.
The (rg1) allele is the only non extinct allele associated with rugose (rg). This allele is hypomorphic with a slight rough appearance at 17??, but moderately rough at 25??. Depending on the severity of the roughness, the eye is classified into mild, moderate, and severe classes. The (rg1) allele deals with loss in memory similar to rugose (rg), in addition to learning disability. On the other hand, (rg7) has the same phenotypes seen as rugose (rg), but differentiates by having a mutation of eclosion delay.
Molecular characteristics of the gene and gene product
rugose (rg) is responsible for the regulation protein kinase A and targeting the membrane. Pathways predicted to direct memory formation are anesthesia-resistant memory and protein synthesis-dependent. With the membrane it may or may not include surrounding organelles associated proteins. Its identity of being required for retinal pattern as well as, interactions with epidermal growth factor receptor (EGFR) signaling pathways links to learning, short-term memory loss, neuromuscular junction, and their body. Short-term memory impairment is one of the main discrepancies caused in this gene by the absence of cold shock. This deficiency is seen at three hours after one cycle training. After every three hours more deduction in memory is seen to occur (Qin, 2013). At the molecular level, it is said, in the pathway of memory formation theirs a direct link which connects dysfunction in short-term memory into long-term memory (Zhao, 2013). Pathways predicted to direct memory formation are anesthesia-resistant memory and protein synthesis-dependent (Zhao, 2013).).
The mutation of rugose (rg) primarily causes abnormal or complete loss of cone cells. This can be retrieved by proapoptotic signals. However, a complete rescue can only be completed by Notch signaling. Cone cell loss is also seen by N-terminal kinase activity and reduction of EGFR signaling pathway. Together, both these aspects accumulate in integrating various signals for accurate regulation of cone cell development.
The biological and molecular perspective of Drosophila melanogaster leads up to gaining insight on different genes and their specificity on how they function and various mutations they cause to help scientists understand what they are experimenting with. In such a case, rugose a protein A kinase induced allele has been evident to be seen in 58 other alleles that are crucial in learning, mushroom body development, and neuromuscular junction development. Studying gene rugose (rg) further, can help gain knowledge on cone cell abnormality in the Drosophila as well as memory loss and learning impairment. Even though, there is no research that rugose (rg) has yet a significance in human diseases currently, Drosophila argose (aos) share similar phenotypes that are visualized in Drosophila rugose (rg). argos also, a protein coding gene located on chromosome 3 functions In enlargement of cell size as well as the development of the optic lobe located in the midbrain of the Drosophila melanogaster. While this gene affects cell size and the midbrain it is also important in photoreceptors of the eye and is hypomorphic as rugose (rg1) (Shamloula, 2002).
With ongoing research, the various functions and perspectives that play a part in the abnormality of cone cells in the retina, and memory loss disability have gave scientists the access and knowledge of rugose mutations that can be observed in other Drosophila flies. Research supports the idea that short-term memory is always associated with long-term memory and factors into olfactory attributes as well. Furthermore, this condition of memory impairment is still inconclusive due to rising alleles which develop and are complemented with others for further research.
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