Diverse Populations and Analysis

Melanogaster Stubble Gene

The author of this scientific report has been asked to offer a thorough review of the stubble gene if a D. melanogaster. Items that will be covered will be a brief overview of the stubble gene, an introduction to the gene, the basic biological process when it comes to the gene, the phenotypic characteristics of the gene, the mode of inheritance of the gene, at least two mutant forms of the gene, the possible chromosomal effects of the gene, the molecular characteristics of the gene and any conclusions that can be drawn from the above. While some may not be interested in the stubble gene in question, some of its attributes and behaviors are quite fascinating and intriguing.

Analysis

Introduction of Gene

First off, the fly in question when it comes to all of this analysis can more easily be referred to as the fruit fly. This is the layman term for D. melanogaster. The symbol for the gene in question is Dmel/sb. As the introduction might suggest, the name of the gene is Stubble and it is a protein coding gene according to the Flybase database. It is also commonly referred to as sbd and Sb-sbd. According to the gene snapshot part of the Flybase record, there is not enough data to summarize the gene's function, at least as of June 30th, 2016. The gene belongs to the peptidase S1 family. The cellular components of the gene in question include a membrane and a plasma membrane, as offered by the Flybase record of the gene. The stubble mutation refers to bristles that are not as long as they normally are on a fruit fly. They are also wider and thicker than with a normal fruit fly.

The strains and variations of the gene are common and easy to find. Indeed, a study done as far back as 1988 used more than one hundred variations and strains of the gene. In that instance, they were tested for the absence or presence of P-Element sequences. This was verified using molecular probes. The timeline of the strains was more than half a century, sixty years, in total. These molecular characteristics as observed in the strains has led to the conclusion that the P-Element status and structure of the genes have changed decidedly over the years in the form of an "invasion" and this has manifested all over the world including in Europe, Africa and the rest of the world as well (Anxolabhere, Kidwell & Periquet, 1988).

The above covers the basic attributes and facets of the gene in question. Now that this is out of the way, other interesting things can be covered as well. When it comes to the topology of the subcellular facets of the gene in question, there is the topological domain, the transmembrane and another topological domain. The former of those two topological domains is the cytoplasmic area. The latter of the two is the extracellular area. The intermediate transmembrane is helical in nature and is a signal-anchor or the type II membrane protein. The amino acid modifications that are present in the fly include a couple of disulfide bonds, four in total, and two glycosylation parts (Uniprot, 2016).

An NIH study that has come out over the years was actually updated this past May. The data they used in their summary is straight from the aforementioned Flybase repository. As explained in other sources, the gene in question is a protein coding gene. Its lineage includes a number of different notable classes and strata and these include eukaryote, sophophora, ephydroidea, Diptera, Neoptera, Hexapoda, Metazoa, among others (NIH, 2016). Beyond that, there are other genes within the Flybase and other data collections that are quite similar to the one being focused on in this report. For example, there is a stubble gene under the D. pseudoobscura realm (Flybase, 2016).

Biological Process & Attributes

As for the biological attributes and parts of the gene, there are a couple of things going on. One important thing to look at are the protein features of the gene. These include a peptidase S1/PA clan, a Peptidase S1A/chymotrypsin family, a serine protease/trypsin domain, a serine protease/trypsin family with a serine active site. The overall molecular function of the gene is within the serine-type endopeptidase activity realm (Flybase, 2016).

Mode of Inheritance

A study by Colby College explains a few things that are relevant when it comes to the subject being covered in this report. First, it is common for fruit flies to be studied in lab situations due to the massive amount of genetic variations and mutations that occur. Indeed, the "mis-expression" of genes with fruit flies are quite common and are easy to study and replicate over time. The fruit fly has four sets of chromosomes. These sets are X/Y, 2, 3 and 4. The strains that manifest with these fruit flies are all over the place in that they include mutant strains (as noted above) as well as transgenic strains. These flies are bred and replicated in laboratories, typically at about 25 degree Celsius, which equates to about 77 degree Fahrenheit. Legs are laid and they hatch in 10 to 14 days. There is about a four to five-day cycle for the larva to grow and pupate and another four to five days before the adult fly emerges from what is known as its pupal case. This is known as eclosion. The aforementioned "transgenic" flies are those that are created through wild-type DNA sequencing (Colby, 2016).

Phenotypic Characteristics

A phenotypic review of the fruit fly shows even more possible variations when it comes to mutations and the expression (or mis-expression) of genes. The bristles alone, the focus of the stubble gene, can take on many different manifestations depending on the behavior of the genes in question. Indeed, they include achaete, bobbed, downy, forked, frizzled, hairless, hook, micro-chaete, prickly, reduced, reduced/scraggly, shaven, singed and so on (CGS Lab, 2016).

Mutant Forms of the Gene

The phenotypes that are included with this gene include embryonic/larval cuticle, the ventral thoracic disc, the adult sense organ, the wing vein L4, the ocellar bristle, the larval thorax, the anatomical cluster and the larval tagma (Flybase, 2016). Two of the mutations that have arisen when it comes to the stubble gene include defects in the apical cell shape. These changes are massive and important when it comes to the evagination of the leg imaginal disc and this leads to defects in assembly and extension of the parallel actin bundles in growing mechano-sensory bristles. There are also bristle phenotypes that occur in both the recessive and dominant iterations of the gene (Hammons, 2005).

Chromosomal Effects

When it comes to the chromosomal effects of the stubble gene, there are a few that are easily identifiable. For one, there is a rapid adaptive fixation of a new favorable mutation, per some work done for the National Institute of Health (NIH). The study notes that general evolutionary theory predicts that the chromosomal region in question would have a lower level of genetic variation and an excess of rare alleles. Experiments that have been done to verify this theory have largely confirmed this to be the case. In experiments where the novel gene does not exist, the overall manifestation of genetic variation is consistent and in line with the recurrent deleterious mutations, as mentioned earlier in this report (Nurminsky, 2001)

Functions & Products of Stubble Gene

Finally, one has to realize and understand the basic functions and reasons for the stubble gene existing in the first place. As explained by Appel et al., the "stubble-stubbloid (Sb-sbd) gene is required for hormone dependent epithelial morphogenesis of imaginal discs of Drosophila, including the formation of bristles, legs and wings (Appel et al., 1993). Overall, the function of the gene takes on two main forms. The first is that it acts through its proteolytic domain (which is extracellular in nature) to detach imaginal disc cells from matrices. The second is that is transmits an onside to inside signal to the intracellular domain so as to modify its cytoskeleton and also facilitate cell shape changes via its underlying morhpogenesis. The translated protein involved in all of this is a 786-residue type II transmembrane protein. There is an N. terminus in and a C. terminus out. Included with that is a N-terminal domain of nearly three dozen residues and an extracellular C-terminal domain that is trypsin-like in nature (Appel, 2016).