Previous Story: The Playground
Josh sat in bed enthralled, while watching "Return of the Jedi" with his father. Hypnotic “Star Wars” pictures of Yoda and Luke flashed on the screen before them.
Yoda: That face you make... look I so old to young eyes?
Luke: No. Of course not.
Yoda: I do. Yes, I do. Sick have I become, old and weak... When 900 years old you reach, look as good you will not, hmm?
"Pa! Is Yoda really 900 years old? Can you become so old?" asked Josh.
"I don't think that I'll ever become, or even want to become so old,” laughed Rosh, “I'd rather be me, than Ashvathama or Yoda."
"When my time is up, I'd rather go. And don’t you try and stop me young man, if I ever turn into a live vegetable."
"I don't know about Yoda, but there are many microorganisms that are ageless. We humans age but Hydra, for example, doesn't."
"So, there are some microorganisms who never 'become one with the force' because they never age."
“What’s a Hydra Pa?” asked Josh.
“Hydra are very small, simple, fresh-water animals that can be found in most unpolluted fresh-water ponds, lakes, and streams in temperate and tropical regions. Let me show you one on YouTube in pond water."
"Biological aging happens at two levels,” Rosh continued answering his son’s question, after they had watched the Hydra among other microscopic creatures in one drop of pond water, “one at the level of my whole being which you call Pa, and another at the part level of my individual cells that make up my body.”
“The age of my whole body is different from the age of my individual cells just like the age of your toy car may be different from the age of its individual parts. Say your toy car is a couple of years old, and its wheel breaks. I get you a new wheel to repair it. Your car will still be two years old, but your new wheel will be newer than the car.”
“Similarly, even though I am so old, some of my cells have just been made. They are barely a minute old. Human cells produce new cells by subdividing themselves. Our new cells are constantly replacing our dead ones.”
“From inception to puberty, more cells are made and less die, so you see the human body growing fast. Then they attain a kind of equilibrium up until old age, when more cells die and less are born. That’s why you can see some people shrink a bit in old age.”
“In 1961, a US scientist called Leonard Hayflick showed that a population of normal human fetal cells in a cell culture will divide between 40 and 60 times. So, the Hayflick Limit was coined to describe the restriction on the number of times a normal human cell population will divide until cell division stops.”
“Why do cells stop dividing Pa?” asked Josh.
“Well, Hayflick suggested that the telomeres associated with each cell's DNA get slightly shorter with each new cell division until they shorten so much that they can shorten no more. When that happens, they stop dividing.”
“DNA is sometimes called the map of life,” said Rosh, “because it contains the code, or instructions for how a living thing or a cell is built up."
"DNA is made out of two long, twisted strands like the two strands of an intertwined rope."
"These ropes are mirror images of each other or like a picture and its negative. They contain complementary genetic information.”
“A gene is a part of this DNA code on the rope. It is passed down from both parents to their children."
"Genes are what give kids their unique features like black or blond, curly or straight hair or blue or brown eyes.”
“Your genes are part of what make you the person you are. You are different from everyone alive now, from everyone who has ever lived, and probably from everyone who will ever live except when and if you get cloned. Cloning is like photocopying you in full 3D using a 3D printer, and some.”
“Genes are organized and packaged in units called chromosomes. Humans have 23 pairs of chromosomes. As I said before, one set of chromosomes for each pair comes from a person’s mother, and the other set of chromosomes comes from the father.”
“The two sets of chromosomes you get from the two parents zip up in a pair like the two sides in a zip. You are only one part of an unbroken chain of life, but because of the way the two chromosomes have been zipping up to form a new chromosome from time immemorial, you are unique.”
“Now you can begin to understand telomeres. You've seen what happens when you bleed. A kind of hard dried blood cap forms on your wound sealing off the injury so more blood can't get out and harmful stuff can't get in through the cut made in your skin.”
“Each of our cells must divide according to the DNA map or code passed on to them by our older cells. Sometimes however, some cells aren't able to follow the map correctly and so when they form the body can't recognize them as its own cells. These are called Cancer cells.”
“These cancer cells are strangers to the body even though they were formed within the body. Our body is like a fort, with our protective armies patrolling around on guard duty everywhere to seek out and destroy strangers that could potentially harm us.”
“So when our armies find these mutated cells within us, they check them to see if they are harmful to us. Some Cancers harm the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors.”
“Other Cancer cells can also spread to other parts of the body through our blood and lymph systems. And then multiply or turn others bad, like one bad apple turns its neighboring ones bad. If our armies thinks they are harmful, a fight begins between them and the mutated cells.”
"Are some cancer cells harmless to us as well?" Josh asked.
"Ya, some can be,” answered Rosh, “They are called benign. The ones that our armies think are baddies, are called malignant. Sometimes the armies can also make a mistake in determining whether a mutant cell is good or bad for us, just like you make a mistake in judging something sometimes.”
“Anyway, once the chromosomes within a cell have been copied and the cell divides, telomeres come in play. They are like the dried blood caps that seal the cell’s cuts, to protect them from losing their maps, and from the baddies, and from trying to join up with neighboring chromosomes that are also dividing.”
"So coming back to ageing and death, Biological death of a living thing can happen when they reach such an old age that one or more of their essential parts give up so completely that they can't be repaired anymore. Or living things can also die from disease or injury even while they are not too old.”
"We call living things that go on living forever, Biologically Immortal, and the decay and deterioration caused by old age is called Senescence."
"Metabolism is the life-sustaining chemical changes that happen within the cells of living things. So technically speaking, Senescence stops our Metabolism to kill us."
"But why doesn't aging kill Hydra Pa?" Josh’s curiosity knew no end.
"Another day," Rosh yawned and said. He kissed his son good night and got out of his bed, "It's late now, and I've got to go work early tomorrow. Ask me about it tomorrow night."