Rosana Fernandes da Cunha

Ensaio opcional - 10/03/17

The central dogma of molecular biology, proposed by Crick in 1958, deals with the transmission of genetic information in biological systems. In this flow of information the same message is encoded from different ways. However, as dogma itself has already emphasized, and several studies of this phenomenon later, once this information has passed into protein, it cannot be further recoded into RNA or DNA again. An amino acid (unit that forms the proteins) can be encoded by more than one codon (triplet of bases). In observing amino acids, it is noted that the nucleotides of the third position of the codon undergo a high mutation rate (mainly because of the conformation of the ribosome in the third base, which facilitates the modification of the last nucleotide of the triplet), and this change may or may not generate a new amino acid in the protein sequence. For example, proline can be encoded by four different codons (CCA, CCC, CCG, CCU), if only the nucleotide of the last position undergoes a mutation, the amino acid will remain proline and there will be no change in the formation of the protein. This process will create a "noise" in genetic analysis. But what these different rates of mutations in the nucleotides of an amino acid can tell us about the dogma? Who performs and undergoes evolutionary pressures are the proteins and what they do. Its genetic sequences are less conserved and susceptible to higher mutation rates, which makes it difficult for a protein to decode the genetic sequence of RNA and/or DNA that gave rise to it, corroborating the premise of dogma that the transfer of information from proteins to RNA or DNA does not exist. From the above, it is concluded that, despite more than 50 years of its formulation, central dogma remains crucial in the interpretation of molecular phenomena and serves as a subsidy for current (and future) works on the transfer of genetic information.

Ensaio Opcional - Revisão por Alfredo:

The central dogma of molecular biology, proposed by Crick in 1958, deals with the transmission of genetic information in biological systems (Não parece ser a ideia central, Topic sentence). In this flow of information (virgula?) the same message is encoded from ("From" -> "in") different ways. However, as (the) dogma itself has already emphasized, and several studies of this phenomenon later, once this information has passed into protein, it cannot be further recoded into RNA or DNA again. An amino acid (unit that forms the proteins) can be encoded by more than one codon (triplet of bases). In (Retirar o "In") observing amino acids, it is noted that the nucleotides of the third position of the codon undergo a high mutation rate (mainly because of the conformation of the ribosome in the third base, which facilitates the modification of the last nucleotide of the triplet), and this change may or may not generate a new amino acid in the protein sequence (Talvez esta seja a ideia da Topic sentence). For example, proline can be encoded by four different codons (CCA, CCC, CCG, CCU), if only the nucleotide of the last position undergoes a mutation, the amino acid will remain proline and there will be no change in the formation of the protein. This process will create a "noise" in genetic analysis. But what these different rates of mutations in the nucleotides of an amino acid can tell us about the dogma? Who performs and undergoes evolutionary pressures are the proteins and what they do. Its genetic sequences are less conserved and susceptible to higher mutation rates, which makes it difficult for a protein to decode the genetic sequence of RNA and/or DNA that gave rise to it, corroborating the premise of dogma that the transfer of information from proteins to RNA or DNA does not exist. From the above, it is concluded that, despite more than 50 years of its formulation, central dogma remains crucial in the interpretation of molecular phenomena and serves as a subsidy for current (and future) works on the transfer of genetic information.

Comentários gerais:
- A ideia central foi bem escolhida. A discussão sobre código degenerado é bastante pertinente e interessante para o tema que estamos trabalhando. A ideia geral passada pelo parágrafo esta bem embasada em conceitos fundamentais da biologia molecular.
- O parágrafo não possui uma Topic sentence. Isso dificultou identificar qual a mensagem central apresentada ou defendida no texto;
- A ideia central aparece no meio do texto e sem muita relação com as frases anteriores. A ideia de discutir o código degenerado apareceu de surpresa, talvez pudesse fazer parte da primeira sentença do parágrafo;
- Algumas frases longas dificultaram a compreensão. Maior números de pontos podem auxiliar nesta questão;
- Os pontos discutidos no desenvolvimento não remetem de forma clara e direta à conclusão. Algumas frases apresentadas no texto não adicionaram informações necessárias para a compreensão da ideia central. Tais informações a mais desviam o foco e diluem o poder dos argumentos centrais.

Ensaio 1 - 17/03/17

Proofreading is a repair performed by DNA polymerase itself, in this process it detects whether a nucleotide has been added incorrectly, removes it and adds the correct one before continuing DNA synthesis, but not all polymerases have this function. Why does it happen? What would be the advantage of not having a repair tool? It sounds crazy! When we think that many degenerative and lethal mutations cease to be expressed because the repairing machinery, it is even difficult to believe that there are organisms that "prefer" not to have it in their composition. However, they do exist! Some Bacteria and Archaea do not present proofreading in their DNA polymerases. For these organisms, which want to have a gigantic population, maintaining mutation errors can be beneficial. How can this be positive? The number of organisms in these populations is very large, the conservation of high error rates can end up generating a "successes" that, from generation to generation, becomes an evolutionary gain. Due to the large number of individuals in these populations, this process ends up being feasible, since the loss of organisms does not affect their maintenance. The eukaryotic repair machinery, however, is more refined. Because they are smaller populations, they can not afford the "luxury" of losing their organisms, this diminishes the reproductive power and the gene flow among individuals, which can lead them to extinction!

** Revisão por Lyslaine Sato

A ideia to texto foi bem desenvolvida
Os questionamentos ao longo do texto proporcionam uma discussão interessante e uma abordagem informal ao tema, que deve ser adotado com cautela de acordo a finalidade do texto
Poderia ter sido utilizado ponto final ao expor o seu topic sentence.

Ensaio 2 - 24/03/17

A teoria neutra propõe que padrões existem sem a necessidade de seleção natural, e são causados apenas por eventos estocásticos. Kimura (1968) propôs que as variações encontradas nos organismos são formadas a partir de processos de mutações e deriva genética, não por seleção natural. A deriva genética são mutações aleatórias ao longo do tempo, evento estocástico, que levam a um resultado mais ou menos previsível. Ou seja, você sabe o que vai acontecer, mas não sabe a trajetória exata deste acontecimento. A teoria neutra permitiu que fossem criadas hipóteses para substituições moleculares. A hipótese nula é que essa substituição é neutra, ou seja, não adaptativa. A hipótese alternativa é de que ela é seletiva, ou seja, tem valor adaptativo, gera alguma alteração que beneficia o organismo.

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