What is universal in Molecular Biology?
The central dogma of molecular biology is claimed to be universal, including all possible ways to process biological information. DNA, RNA and proteins are the key sources to maintain and move information forward. Transfers are based on replication, transcription and translation, including well-known mechanisms and some less understood pathways. Since its original formulation, the concept was expanded to include multiple possibilities. Consequently, the power of dogma's universality is to predict information flow in any condition. Additionally, if the dogma is universal, comparisons among organisms are possible, providing bases for phylogenetic and evolutionary investigations. In contrast, the genetic code is not universal, thus different organisms exhibit distinct modes of translation for numerous reasons. However, what may be a problem to establish general patterns also addresses very interesting questions about the evolution of the genetic code in different lineages. Finally, if universal or not, these very solid patterns in molecular biology are the crucial background to understand and study the diversity of life.
Correção por Domingo:
A sentença introductoria não é muito explicativa. Durante a leitura do texto enteiro não queda muito claro qual é o tema principal do texto. Só queda bem claro quando lé o titulo.
O comprimento das sentenças é correito.
Quando usa a palavra "Transfer" na frase "Transfers are based on replication, transcription and translation, including well-known mechanisms and some less understood pathways." parece que esta a falar de algum proceso biologico especifico. Igual é melhor escrever "Biological information is transfered based on replication…."
DNA replication and dichotomy thinking
In a very complex dichotomy, DNA duplication is the molecular process to make two double-strand molecules from a single one. Other complex dichotomic examples are endless, including behavioral decisions, reproductive strategies and use of environmental resources. Could DNA replication be related to the role of dichotomy in our tree thinking? The answer to this question is not simple, but some aspects of molecular evolution can explore this issue. Firstly, replication process is vital to life maintenance, assuring two new copies from a single model. Secondly, dichotomy in cellular biology also plays vital role in cell division. Expanding this pattern, heritage can be conceived as sequential dichotomies where each new generation is doubled compared to the previous. In a phylogenetic perspective, lineages are split into two through time in a historical dichotomic process (cladogenesis), which is central to our view of evolution and historical reconstruction. In other words, DNA replication, even in a small scale, has crucial importance to vertical heritage. Consequently, the methods and premises we currently use for historical inference of life are deeply linked to this dichotomic process.
Comentários da Flávia:
Gostei muito das palavras que você usou para ligar as frases. Achei bom o tamanho das frases também, não muito longos.
Eu só começaria a primeira frase direto com "DNA duplication is…" pois acho que dá mais força a sua frase.
Achei muito didática a forma como você escreveu em geral, muito bom :)
The major roles of genetic drifting in molecular evolution
Neutral theory in molecular evolution provides a simple explanatory framework to high divergences of substitution rates. The theory does not evoke natural selection to explain most patterns of diversity at the molecular level. In contrast, it simply assumes that stochastic events are responsible to the divergence of nucleotides. At first, this assumption may be surprising, but several lines of evidence corroborate this view. As mutations are mostly neutral or nearly neutral, genetic drift determines the likelihood of fixation. Of course, natural selection plays crucial roles in purifying and selecting mutations that increase fitness. Nevertheless, this process is far more restricted in terms of genome remodeling. As predicted by neutral theory, genetic drift is the major process driving molecular evolution.
Comentários Ana Laura
Texto com frases curtas e claras.
Você deveria substituir na frase “…responsible to the divergence of nucleotides….” ´to´ por ´for´.
Acho a frase "…At first, this assumption may be surprising, but several lines of evidence corroborate this view…" desnecessária.
Gostei muito do texto.
Audience: graduate students of biological sciences
Implications of effective population size in genetic drift
Genetic drift is an evolutionary process which magnitude is deeply related to effective population size (Ne). Considering the stochastic nature of this process, alleles frequencies float randomly until fixation or lost throughout generations. According to Ne, the impact of genetic drift can be dramatic. When Ne is high, genetic drift is buffered and alleles take long time to become fixed or lost. This pattern is expected even when the initial frequencies are different. On the other hand, when Ne is low, frequencies rapidly change and soon become fixed or lost. Consequently, reduction of Ne profoundly affects alleles fate. In contrast to natural selection, which magnitude is imposed by fitness, genetic drift is severely changed by Ne. Finally, molecular evolution is mostly driven by genetic drift and, consequently, Ne should be taken into account as a key factor modulating the impact of genetic stochastic processes.