Answer to yesterdays Pop Quiz: Intelligence Quotient (Mental Age divided by Chronological Age times 100).
The ability to curl your tongue is genetic. Either you inherit the Dominant tongue-curling gene, and can curl your tongue, or you inherit two Recessive genes, and cannot curl your tongue.
In my classes I use my wife's family to show how genetics works, and the Dominant/Recessive aspect of genes.
My mother-in-law cannot curl her tongue (2 Recessive genes). My father-in-law CAN curl his tongue (at least 1 Dominant gene). My wife cannot curl her tongue, which means my father-in-law has one Dominant gene and one Recessive gene. My wife inherited a Recessive gene from both parents. Neither her brother or sister can curl their tongues, either. They all inherited two Recessive genes, even though they all had a 50/50 chance of inheriting a Dominate gene.
My daughters can curl their tongues. So, they got a Dominant gene from their father.
That is three generations. How about the 4th generation?
I have been asking my grandson all of his life if he can curl his tongue. At first, he couldn't. The question was whether or not he was too young to understand what I was asking of him, so I kept asking him. He is 4 years old now and...
he curled his tongue several months ago!
Back to my wife (his Grams), who cannot curl her tongue. Last week my grandson tried to teach her how to curl her tongue. "It's simple, Grams, just stick your tongue out and do this." She can't, and won't be able to. Why? She has two Recessive genes.
What if I decide that the ability to curl one's tongue is a sign of a superior race, and I want all of my kids to be able to curl their tongues. What do I do? I marry a woman who can curl her tongue, too.
POP QUIZ: Is that a guarantee that my kids will all be able to curl their tongues?
Shake your head no.
Why? Because I or my wife might have a Recessive gene. It only takes one Dominant gene for the trait to show up. What if both of my wife's parents can curl their tongues, and both of my parents can curl their tongues? Does that guarantee it?
Still no. Same reason.
So, those couples who go to one of those "boutique sperm banks" and buy the sperm of a genius for invitro fertilization, or go to a one of the banks offering already fertilized eggs and buy the zygote of a man and woman who are both a genius, does not guarantee that they will have a genius?
No. Why? There might be a "dumb" Recessive gene hiding in there that is inherited instead of the genius gene.
Actually, no "genius" or "dumb" gene has been found. But, a "dumb gene" would explain a lot of people I have known.