Juan Jimenez Merino

Aula 01: Estrutura da Informação Genética

Ensaio opcional (10/03/2017):

In molecular biology, the central dogma refers to an explanation proposed by Francis Crick in 1958, regarding how information flow occurs in biological systems. It states that three types of biopolymers (DNA, RNA and protein) harbor embedded information encoded in a specific sequence of subunits. The information contained in these sequences is transmitted unidirectionally via two enzymatic processes: First, transcription, where genomic DNA chains give rise to RNA strands; and second, translation, where RNA sequences are transformed into proteinic chains based on an established code of nucleotide triplets. Multiple divergences from this sequential flow can be found in nature. However, the central dogma still holds as a general frame in which all living organisms can be compared. Current historical reconstructions of lineages are built under the assumption that both, environmental pressures and time, promote change in biopolymers across generations. Nevertheless, the details that render this assumption true may vary greatly across organisms. Some radical examples of this variation are change in translation signaling, deviant information flow between biomolecules and acellular evolution. In consequence, future discoveries in molecular evolution may rely on defining the central dogma, not as a biological constraint, but as a methodological framework.

Comments

Your text is well-written. I could identify all the main sentences and topics that you pretended to transmit. Your sentences are not long and transmit information in a very objective, clear way. Beyond that, your English is very good. I can see you have a vast vacabulary and knowledge on grammar, what makes your life easier when writting a scientific text in this language. In general, I do not have any complains about your text. Very nice job! (commented by Caio Gueratto).

Aula 02: Replicação e Reparo

Ensaio 1 (17/03/2017)

There are two methodogical issues to be taken in consideration when creating a molecular history reconstruction. These are assumptions that underlie current phylogenetic techniques: Vertical flow of heredity and universal dichotomy. The former deals with how DNA is transferred, while the latter has to do with the separation of populations. In an applied context, this means that events that are considered noise in data processing could be highly informative. In the first case, phylogeny resolution is obscured by the occurrence of horizontal transmission. Evaluating patterns of transmission and incorporating them into reconstruction models is a challenge that still is to be addressed. On the other case, assuming dichotomy as a universal constraint in evolution could prevent the discovery of natural polytomies, as rare as they could be. One hypothetical example that comes to mind is the one of a drying lake. During this natural event many isolated pools could arise simultaneously. Each pool would then give origin to an isolated population of aquatic animals, which would then evolve independently. To propose the existence of such events, external evidence has to be provided, since current methods would assume its molecular trail as lack of resolution. Hence, difficult examples of tree reconstruction could be helped by new methods that deal with unusual evolutive events.

Comentário

Você descreveu de modo sucinto as questões relativas a problemas discutidos em análise filogenética e acrescentou exemplos. Acho que foi direto ao descrever os fenômenos que se propôs a descrever. Você esqueceu o "lo" em Methodological. E uma critica: Penso que você não deveria usar o termo "has to do". Parece muito informal aqui. Mas como disse achei direto e sucinto nas explicações.

Aula 03: Teoria Neutra

Ensaio 2 (24/03/2017)

Giving differential weight to characters is a constant dilemma in phylogenetic reconstructions. The issue arises when observable traits can be selected or given a certain value. Usually, the criterion applied for this practice is whether the trait is informative or not. The resulting reconstruction could be a better resolved one. However, it is possible to argue that this means taking away objectivity from the process. This arises from the fact that assumptions have to be made regarding the evolutionary history of the system. For example, how much selective pressure has been acting over a given site over the course of time. If that´s the case, mistakes can be made in order of achieving resolution. On the other hand, practice has proven this tool to be useful. As a result, decision making has remained a strong component, even among the most established methodologies of molecular biology.

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License