Ensaio opcional (10/03)
The discovery of the tridimensional structure of the DNA marked the beginning of the study of how this molecule can lead to the formation of a protein. Francis Crick proposed, then, the Central Dogma of Molecular Biology, which states a linear flux of the genetic information. Primarily, it is stored in the DNA molecule, that leads to the formation of a RNA molecule, which is “translated” by the ribossome into a protein by the use of a code, called “genetic code”. Crick received some criticism regarding the use of the word “Dogma”, because it was argued that it would be a “non scientific” word. However, researchs developed since the proposal of the Dogma confirmed the almost universality of the genetic code, along with some special cases, like the capacity of the RNA to form DNA or another RNA. Interesting and intriguing questions are still waiting to some response, like the universality of the code itself (that is, why it is universal) and how it could have arised and evolved.
Aplicando os critérios sugeridos pelo Daniel, creio que sua primeira frase não vai direto ao ponto, não se enquadraria como um "topic sentence".
Suas sentenças são curtas e precisas, isso é bom.
No mais, o seu texto apresenta uma contextualização histórica da discussão em torno do dogma central que foi fácil de fácil entendimento.
Ensaio 01 (17/03)
The mismatch repair is one of the most important mechanisms to fix the DNA strand. It consists in the substitution of a region that is near a mismatched base in the DNA sequence. The process begins when a protein complex recognizes a base that do not pair with the complementary base, located in the opposite strand of DNA. After that, a second complex cut the region that is neighboring this incorrect base. Finally, the DNA polymerase connects the correct nucleotides in the chopped strand. A special enzyme called ligase binds these newly added nucleotides together, restoring the DNA molecule. This mechanism is widely distributed in prokaryotes, although it can also be found in eukaryotes. It is proposed that, in these organisms, the mismatch repair mechanism originated via lateral transfer from mitochondrial genomes.
Oi Bruno! Em geral achei seu ensaio bem escrito. Você utiliza bem o "topic sentence", mas me deu a impressão de que às vezes a propria frase fica cortada por virgulas. Por exemplo: "It is proposed that, in these organisms, the…" Seguindo as sugestões do professor, seria bom repensar essa frase tentando evitar o uso das duas virgulas. Eu também tendo a escrever com muita virgula e percebi que é porque eu vou falando a minha ideia e escrevendo ao mesmo tempo, isso me leva a botar virgula cada que eu paro de falar… Talvez ajude!
Uma última dúvida: Será que ficou faltando um "WAS" nesta frase: the mismatch repair mechanism "WAS" originated via lateral…
Juan Manuel Vidal
Ensaio 02 (24/03)
The neutral theory of molecular evolution proposes that the majority of the mutations do not affect the phenotype of the organism (Kimura 1968, King & Jukes 1969). Kimura proposed this idea measuring the rate of nucleotide substitution of the hemoglobin gene. He discovered that this value is much higher than the expected. The only explanation is that the majority of this mutation can only be neutral. Before this finding, researchers thought that the mutations only fix in the genome due to its adaptive value. The proposal of the neutral theory lead to the development of the concept called "genetic drift". It proposes that stochastics processes drive the evolution of genetic sequences. In this sense, selection could have only the purpose of removing deleterious mutations. This type of selection is called "purifying selection".
Kimura, M. 1968. Evolutionary Rate at the Molecular Level. Nature, 217:624.
King, J.L.; Jukes, T.H. 1969. Non-Darwinian Evolution. Science 164:788-97.