How genes shape who we resemble

Sunday June 3, 2012

Q: If genes are supposed to come 50-50 from both parents, why do some of us seem to take so strongly after Mom or Dad?

A: It’s true Mendelian inheritance is basically symmetrical, but don’t forget about "sex-linked" genes, on the X chromosome, noted medical geneticist Carter Denniston.

Females have two X’s and males only one. All of a son’s X-linked genes come from Mom, whereas a daughter’s X-linked genes come equally from both parents.

"So that’s one possible source of asymmetry."

Also, some genes mask the effect of others, by "dominating" over them, such as certain eye colors or hair colors typically prevailing over others, instead of the two colors being averaged.

But more generally, says Denniston, the human traits that are most interesting to us are influenced by many genes and environmental factors acting together, presenting a very complex form of inheritance. Intelligence, height, personality, temperament, mental disease are just a few of these.

Here it is often the case that a child is not a simple average of his or her parents. For these, probably the simplest source of asymmetry to understand is just plain chance:

"Remember, if you flip a fair coin 50 times you expect to get EXACTLY 25 heads and 25 tails only about 11 percent of the time! For the rest, the result is not exactly symmetrical, and can be quite far from 50-50."

Q: In his 1960 "New Yorker" article, novelist John Updike wrote, "Of all team sports, baseball, with its graceful intermittences of action, its immense and tranquil field sparsely settled with poised men in white, its dispassionate mathematics, seems to be best suited to accommodate, and be ornamented by, a loner."

Who was this loner and what was the historic occasion?

A: It was Boston Red Sox slugger Ted Williams’s final game at Fenway Park Sept. 28, 1960 that Updike had attended, says Dorothy Seymour Mills in "Chasing Baseball: Our Obsession With Its History, Numbers, People and Places." Updike praised Williams for his renowned quietness and went on to describe his legendary last-at-bat home run: "From my angle, behind third base, the ball seemed less an object in flight than the tip of a towering motionless construct, like the Eiffel Tower or the Tappan Zee Bridge. It was in the books while it was still in the sky."

Also in the books when Williams retired were 2,654 total hits, 521 home runs, and a lifetime average of .344. He was the last of the .400 hitters, batting .406 in 1941!

With Updike’s headline-like title "Hub Fans Bid Kid Adieu," long-time sports writer Roger Angell deemed his essay "the most celebrated sports piece ever."

Q: How do you cure an anorexic eel?

A: When a three-foot-long green moray eel that had long been kept in a barroom finally outgrew its tank, the bartender donated it to the New England Aquarium. It soon settled in behind the rock work of the tank, as eels often do, says veterinarian Beth Chittick Nolan in "The Eel and the Bartender," included in the book "The Rhino with Glue-on Shoes."

For several days, the eel stayed hidden and refused food -- not uncommon especially after a move -- but this behavior continued despite the aquarists’ best efforts to entice it with live bait, etc.

In desperation, they finally summoned the bartender for help. No sooner had he approached the tank than a small head appeared in the far corner, slowly pulled its lean body in front of the man and began undulating back and forth in a smooth, calm rhythm.

The bartender then hand-fed the eel a piece of fish and from that day on, the eel did not refuse to eat.

"Their bond was even more elemental than the eel’s hunger for food."


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