Regeneration

A. In a recent Hollywood film, a scientist was injected with lizard DNA resulting in the regrowth of his missing limbs. Such a story reflects a real and longstanding scientific quest – to understand the secret of the extraordinary regenerative powers of animals, and duplicate them in humans.

B. If a human were to cut off his arm, he would end up with a permanent stump covered in scar tissue. However, if a lizard loses its leg or tail, it is able to grow a new one. The wound will close and, over time, it will create new bones, muscles, nerves and skin. Healing powers of this kind were first discovered by an Englishman, Abraham Trembley, in 1740. Since then, scientists have discovered more animals with regenerative powers: starfish grow dismembered arms back while some flatworms can rebuild their entire bodies from a single cell.

C. Although there have been centuries of research, we are still a long way from even understanding how regeneration works, much less replicating the feat in our own bodies. This is mainly because many of the most suitable animals for study make poor research lab subjects. Despite this obstacle, we know the basic steps that a regenerating limb must go through.

D. Instead of asking how some reptiles, like lizards, are successful in regenerating limbs, one might equally ask why mammals like us cannot. There are no solid answers, but several theories have been proposed. Perhaps cancers are more of a problem for mammals. The same checkpoints that stop our cells from growing uncontrollably into tumors might also stop a blastema from forming. Enrique Amaya, a developmental biologist at the University of Manchester, wonders if it’s because we are warm-blooded. “If a reptile or an amphibian chews off one of its arms, it could hide away for weeks without eating and regenerate,” he says. “That’s not possible for an animal whose high metabolic rate requires it to feed constantly. It has to heal quickly.”

E. But even if we could understand and replicate the lizard’s regenerative powers, Amaya believes regeneration would be a very lengthy process. Naturally, or in a research lab, it can take 400 days to grow back a leg that is less than 4 millimeters across. The largest ones need more than a decade to complete the regeneration. Human arms, for example, would take much longer than that. However, learning how to close an injury more quickly would perhaps be the most practical benefit of studying the regeneration of limbs in the animal kingdom.

F. The study of regeneration is ultimately about how our bodies produce patterns – how our cells know where they are, and how they organize themselves to make organs. That knowledge will be invaluable, no matter what technique is used to produce new body parts. Regeneration is about taking a few steps back to take many steps forward.

your answers should be in sentences, not short notes.

1. What is the text about/ the main idea?

2. What type of text is it?

3. What is the main idea of each section?

4. Does the writer include facts (statistics, dates, people)? If so, what are the important ones?

5. Does the writer suggest or imply anything? If so, what is suggested or implied?