Philosophy Of Biology Take-home Final (terzis)

Batool Alsamadi Philosophy of Biology TR 2:10 – 3:30pm, Dr. Terzis 12-18-06 [due] Final Exam (Take Home Paper) 1. What are genetic switches? What are embryonic maps? How does the complex relationship between these two ideas shed light on the theory of evolution as Carroll explains it? In a nutshell, three main concepts are covered when it comes to the theory of evolution, when involving genetic switches and embryonic maps below: (1) genes, (2) location genes cover, and (3) genetic switches that control the turning on/off of those genes at those switches. Prior to taking Philosophy of Biology, I’ve personally have never heard of genetic switches before – even Carroll says so himself that the press and lab work has not paid enough homage to the vital role genetic switches play – in fact, only recently have molecular biologist discovered the location and properties of switches. For genetic switches are the reason certain bones longer/thinner than some, and the reasons why certain bones are placed in certain ways before others. Genetic switches control where the genes are used in body tissue, and are the key roles in both development and evolution. Metaphorically, they are best thought of “part artist, part genetic computer.” To be more precise, a genetic switch is a protein structure – a strand of DNA which exercises its influence over that strand. Also, The idea of a genetic switch belongs in the analogy of “dark matter”; like genetic information, dark matter is regulatory DNA which codes for the sequence. Genetic switches are like nerve cells; some switches act like activators, and some act like repressors (e.g. as seen in the lactate repressor gene, which insoforth represses the production of enzyme needed in order to metabolize certain kinds) and thus, some proteins are either activators or repressors. Also, The evolutionary shifts in zones arise threw changes in DNA sequence of genes switches, so

ultimately the cause of some sort of speciation change would be a mutation in the sequence of the gene switch. The anatomy of a squirrel’s body, for example, is built piece by piece, pattern by pattern, bone by bone, and so forth by the encoding of switches dispersed across the genome. A gene can have switches which authorize its assertion in the eyes, finger, and heart. Moreover, “tool kit” genes are in the case of multiple switches that are active in different regions of the developing body. These tool kits are able to know where to act and when, where to shape the development of form – as well as the operating instructions for the tool kit – are all executed from the genetic switch. Building on this, these instructions for the tool kit are embedded in the genetic switches. Switches are what enable different organisms to be created while using the same tool kit – while being unique to individuals. In order to know the region of the organism’s future body part developments, or to know which structures are produced later by the cells in different regions of a young embryo, it led embryologists to have a model called the “fate map.” Fate maps answer all these questions, and reveal the approximate positioning of cells in order to form certain structures. At some stage in the development of these young embryos, a fate map will show the knowledge of cells’ location in an embryo, and for which structure they will belong to. Fate maps are very comparable to that of an actual map or atlas; to illustrate – the particular location of tissues, cells, and organs are like countries that are defined by their longitude and latitude, and some cases when it’s a structure projecting out of the organism’s surface – altitude. The shape of the “globe” will be based on the shape of the particular organism’s embryo (e.g. a frog egg has a spherical embryo while a fly is more oval). The depth of geographical structures are that compared to the layering of the organism’s body. The national identity in the world is that of compared to biological identity: blood cells, heart cells, etc. This technique was developed by marking individual cells, and observing where this particular cell and its daughter cells

ended up. This will reveal the future positioning of the organism’s features defined by the coordinates of the longitude and latitude lines. Based on longitude or latitude, we can break the embryo down and map a variety of different locations. The tool kit gene comes into play when cells acquire knowledge of who they are, and their location. This is why a fate map is a key provider in understanding and determining the location for the surface on the embryo. The relationship between genetic switches and locations on the map is that switches determine the tool kit genes, while genes determine where they’ll eventually be located. Because the fate map will show a variation of different locations, those different locations are governed by different genes that determine for example, whether the feature is an eye or an antenna; thus, the concept of a genetic switch and embryonic map come together. Moreover, this concept relates to the idea of evolution, for it is the core of Evo Devo: the idea which the Theory of Evolution has light shed on it by developmental biology, and illuminated by the fact the genetic switch is able to undergo mutation. According to the Theory of Evolution, there can be mutations in these genetic switches. Since the genetic switch is a protein structure, it would therefore cause a change in the fat map of the embryo. Because tool kit genes are activated in the embryo, they dictate the regions where genes will be turned on and off – which is the central concept to this whole explanation – the genetic switch integrating positional information (latitude, longitude, depth, etc.) is the result of when the integration determines when and where genes are turned on or off in order to create structures and initial structures which are marked by strips or spots on the surface of the embryo. The function of a genetic switch is to integrate information in which then allows genes at a certain position on the surface of the embryo to create a certain structure.