martes, 21 de octubre de 2008
De: Obesidad y Metabolismo: La importancia de "la opinión de tu cuerpo"
De: Obesitat i Metabolisme: La importància de "l'opinió del teu cos"
jueves, 14 de febrero de 2008
They used techniques that are normally used in genetics. To study genetics, family lineages are useful tool. There are some complete family lineages in Harry Potter books, most notably the family around Sirius Black, a family that can look at hundreds of years of „toujours pure“ magical tradition. In this family, just one case of non-transmission of magical abilities has been reported, this resulted in a squib offspring. When it has to be determined whether a disease is based on genetics or on environmental factors, very useful tools are families with twins, like the Weasley or Patil twins. Both are monozygotic and have clearly magical abilities.
Another technique that is frequently used by geneticists are adoption studies. The protagonist himself, Harry Potter, is in such case, as he was raised by the Dursley family, all of them born-and-bred muggles, after the death of his parents, great magicians James and Lily Potter. Although Harry was not aware of his magical capabilities until his 11th birthday, they did not decrease in the muggle environment. However, they are likely to be affected by factors such as experience and emotional state.
Of all the magical abilities described in Harry Potter books, three of them seem to be linked to specific genes and furthermore directly inherited to the offspring. The ability of speaking to snakes (also known as the parseltongue), is known to be a feature of only direct descendants of Salazar Slytherin. Furthermore, Sybill Trelawney, a professor of divination at Hogwarts school, is a seer and so was her great great grandmother. Lastly, Nymphadora Tonks, a character in the fifth Harry Potter book The Order of the Phoenix, was able to change her physical appearance (a metamorphmagus) and so was her son.
The authors hypothesize an epigenetic mechanism. Epigenetics refers to chromatin and DNA modifications that change the expression of genes, but do not involve changes in DNA sequence. The regulation of gene expression is mediated through the accessibility of the Transcription machinery to DNA. The hypothesis is that a profound mutation in an evolutionary ancestor occurred in a histone gene, which radically altered genome wide chromatin structure. Histones are the main protein components of chromatin, the complex that constitutes chromosomes. This created new sites of chromatin accessibility and altered gene regulation, including novel “magical enhancer” elements to drive expression of genes (figure 1) related to magic.
In genetics, an enhancer is a short region of DNA that can be bound a set of transcription factors to enhance transcription levels of genes. A dominant mutation in the histone gene could provide heritability of this epigenetic effect. Such a mechanism originating in our ancestors supports the fact that there are non-human creatures with magical abilities, like for example, house elves, goblins or the centaur. This study clearly shows that some aspects of magic have a genetic basis and that this is rather related to a magical enhancer element than to single gene effects.
domingo, 13 de enero de 2008
De Educació de l'atzar, eduació a l'atzar
De Educación del azar, educación al azar