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AXIS FORMATION

Localizing mRNA during oogenesis is important producing axes and maintain polarity in Drosophila. [1] The mRNA gets localized due to the proteins within the organism. This process is done using microtubules. Localizing RNA also helps produce germline and somatic cells in the embryos future. [1] Microtubules use localization to create the body axes by using three major genes. The first two genes are Bicoid (bcd) and Oskar (osk) which help create the anterior-posterior axis by localizing mRNA. [1] The third gene is Gurken (Grk) and it produces the dorsal-ventral axis.

ANTERIOR-POSTERIOR

In the development of the A-P axis, Bicoid is localized to the anterior side while Oskar is on the posterior. Bicoid creates a protein gradient that determines the head and thoracic regions. Oskar helps produce the poles and the abdominal region with the help of Nanos RNA. [2] Oskar produces a long and short form which comes from start codons. The long form is just used for anchoring while the short form nucleates pole plasm. [2] Bicoid is localized using Exu protein and involves several different proteins to keep it on the anterior side.

DORSAL-VENTRAL

There are two main genes that produces the dorsal-ventral axes and those are Gurken (Grk) and torpedo (Top). [3] The two genes are used for signaling to distinguish dorsal cells. The Toll receptor is used for the asymmetry in the embryo. The Toll receptor is constrained to the ventral region and inhibited on the dorsal due to Grk-Top signaling. [3] Wingless (Wg) and Decapentaplegic (Dpp) are also genes that control the D-V and A-P axes of the wings and legs. [4] Wg is expressed in ventral cells while Dpp is inhibited the same cells, but it is opposite in the dorsal region. Dpp is expressed while Wg is inhibited. [4]

PROXIMAL-DISTAL

While Wg and Dpp plays an important role in D-V and A-P axes, they also are genes that determine the proximal-distal axes of the legs of drosophila. The expression of the two genes are met in the middle of the leg. These two genes encode of three different genes that define the different domains within the legs. Distal-less codes for a protein (DII) that is used for early leg formation, but as the organism matures, DII is only expressed in the distal portions of the leg. [4] Dachshund also codes for another protein that is partially shown in the same domain as DII but helps with the portion that contains the parts of the upper leg like the femur. [4] Extradenticle (Exd) and homothorax (Hth) are expressed in the proximal regions around the hip and connective parts to the body. [4]

ADVANTAGES/DISADVANTAGES

Drosophila is an important model organism for many reasons. They have short generation times, inexpensive and they also have balancer chromosomes. [6] One of those is that drosophila has been important for cancer studies. [5] Researches have picked these organisms due to their variations within their genome, and they can also do large screenings. Drosophila has helped scientists understand many tumor forming genes like Hippo, Notch, Dpp and JAK-STAT. [5] They have also been used to understand genes that cause heart failure. The genes of drosophila is similar to the genes of mammals. A large percentage of human diseases has been found with the drosophila genome. [6] A disadvantage of using the fruit fly is that they are really small, only 3mm in length.

Citations

1)      Steinhauer, J., & Kalderon, D. (2006, April 03). Microtubule polarity and axis formation in the Drosophila oocyte. Retrieved March 21, 2018.

2)      Chang, C., Nashchekin, D., Wheatley, L., Irion, U., Dahlgaard, K., Montague, T. G., . . . Johnston, D. S. (2011, August). Anterior-Posterior Axis Specification in Drosophila Oocytes: Identification of Novel bicoid and oskar mRNA Localization Factors. Retrieved March 21, 2018

3)      Neuman-Silberberg, F., & Schupbach, T. (1994, September 01). Dorsoventral axis formation in Drosophila depends on the correct dosage of the gene gurken. Retrieved March 21, 2018.

4)      Wu, J., & Cohen, S. (1999, January 01). Proximodistal axis formation in the Drosophila leg: Subdivision into proximal and distal domains by Homothorax and Distal-less. Retrieved March 21, 2018.

5)      Miles, W. O., Dyson, N. J., & Walker, J. A. (2011, November 01). Modeling tumor invasion and metastasis in Drosophila. Retrieved March 22, 2018.

6)      Wolf, M. J., & Rockman, H. A. (2008, October 01). Drosophila melanogaster as a model organism for genetics of postnatal cardiac function. Retrieved March 22, 2018.