Random Analogies
"If we think of the genome as sentences, your DNA - or letters - are what is inherited from your father and mother," he continued. "The DNA methylation is like the punctuation marks that determine how the letters should be combined into sentences and paragraphs that are read differently in the different organs of the body - the heart, the brain, and so on. What we've learned is that these punctuation marks are attentive to signals that come from the environment, and that they take cues from living conditions in childhood. Essentially, they act as a mechanism, we believe, for adapting the DNA to the fast-changing world."
"This pulling force is called transpiration pull. The water in the xylem is like a long column. As the top of the column is pulled (transpiration), the rest of the column is pulled with it, called tension. Water can be pulled so high in plants because of the small size of the individual xylem and the cohesive properties of water. The same hydrogen bonds that account for water's high specific heat give water a cohesive property that allows the xylem to act like a contiguous column."

