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Alive & KickingA Lesson from Grandchildren |
Fourteen grandchildren— what a blessing! Our children are good parents, married well and bring us much pleasure.
The grandchildren are all so different except for the last three born. You see, they were all born on the same day via our youngest daughter. Identical triplets? We’re not sure, because the genetic analysis of their DNA has not been done. But as a devoted Grampa John, I confess to you that I can’t tell them apart except one almost always wears some pink, one wears purple and one some green or blue.
(This sounds a bit like true confession, but I’m doing better lately.) When they were little, their left big toenails told their identity, carefully painted in their own color, touched up at bath time with nail polish because it was impossible to know who was who otherwise.
(“Please take off your bootie so I can see who you are.”) Actually, it is easier now because they are fourth graders this year. Perhaps one might say, does it matter what name went with which child when they were small? Yes! They are individuals, each with her own talents, personality, preferences and life to live.
Even on their first day of school, the three each chose to be in a different class.
How can they be so alike, when the other eleven grandchildren look so pleasantly different?
The triplets appear to have come from the same egg and same sperm, which join during fertilization to form a single cell embryologists call a zygote.
The zygote’s cells produced by the first several cell divisions act like stem cells in that if separated from each other, each has the ability to form a complete embryo.
Shortly after the first several divisions, the cell mass begins to exhibit “polarity” (head and posterior) and left-right side orientation.
Identical children are thought to result from one egg and one sperm, therefore, they have the same exact genes and are “physically identical.”
But what about the tremendous variation shown by the other eleven grandchildren?
We can blame this on the mechanisms of meiosis, which is the technical term for cell division found only in the reproductive organs, which produce the eggs (ova) and sperm in mature animals and plants.
During meiosis (making reproductive cells), the genes from the maternal and paternal parent become shuffled so some genes from both sides of the mother’s family and both sides of the father’s family can be inherited by a single child (but still only 50% from the mother’s side and 50% from the father’s side).
In other words, the genes a single child can inherit come as a mix of the genes from all four grandparents.
There is, also, a further variation produced by what is called “crossing over” in which the genecarrying bodies called chromosomes exchange gene-carrying tips or ends with each other. The result of this genetic dance of the nearly one-hundred-thousand genes makes each sperm cell different and each egg cell’s genetic makeup different.
What are the chances you were ever to exist on this earth?
How many children did your mother have? Any other of her 31,000 eggs, which were immature but fully present when she was born and any other sperm cell of the 4.5 billion present when your zygote formed would not be you.
You would look like another member of your family, perhaps; you would be a gal instead of a guy, possibly.
If your mother or father had married someone else or chanced to have never met, then you would have been impossible because you are as unique as your very own genes. There is no one else in the entire world like you.
Well, this may be all too much for our small human minds, but life is precious. It is the greatest gift you have been given.
I’m thankful to have been given the opportunity to exist.
The odds of you having been born are very, very much against you.
You see, without question, you did win the lottery.
Guest columnist John Cooke taught high school biology for 30 years and is pleased to share his insights with our readers.