The power of genetics

There is always a debate about nature (genes) and nurture (environment). Obviously, BOTH play a factor in life. And here is an item I saw in today's Daily Dish. The item is in June 20 under the title, "The Difference."

Sullivan gives an extended quote from an NY Times article.

I've picked a few excerpts below. Check out the whole article, it is a well written science piece.

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Biologists have made a fundamental discovery about how the human Y chromosome, a genetic package inherited by men, protects itself against evolutionary decay.

As part of the work, the scientists have tallied the exact number of genes on the Y chromosome, finding more than they had expected. That and other research has led the researchers to assess the genetic differences between men and women as being considerably greater than thought.
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The decay of the Y stems from the fact that it is forbidden to enjoy the principal advantage of sex, which is, of course, for each member of a pair of chromosomes to swap matching pieces of DNA with its partner.

The swapping procedure, known to biologists as recombination, occurs between the chromosomes inherited from the mother's and the father's side as a first step to produce the eggs or sperm. Not only does that swapping create novel combinations of genes, making each individual different, but it also enables bad genes -- those damaged by mutation or DNA changes -- to be replaced by their good counterparts on the other chromosome.
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A team of researchers led by Dr. David C. Page, a biologist at the Whitehead Institute in Cambridge, Mass., has made a startling discovery. Denied the benefits of recombining with the X, the Y recombines with itself.

The Y chromosome is made of a single DNA molecule that is 51 million units of DNA in length.
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By making a hairpin bend in the middle of a palindrome, the two arms can be brought together, aligning two long stretches of almost identical DNA sequence. That is the same step that precedes recombination between the maternal and paternal members of each ordinary chromosome pair, which also have almost identical sequences.

In the case of the Y, the alignment of the palindromic sequences leads to gene conversion. A mutated gene on one arm of the palindrome can be converted to the undamaged sequence preserved on the other arm.
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The finding of 78 active genes on the Y contradicts an earlier impression of the chromosome as being a genetic wasteland apart from its male-determining gene. But if the Y is not a wasteland, important consequences ensue for the differences between men and women.

As often noted, the genomes of humans and chimpanzees are 98.5 percent identical, when each of their three billion DNA units are compared. But what of men and women, who have different chromosomes?

Until now, biologists have said that makes no difference, because there are almost no genes on the Y, and in women one of the two X chromosomes is inactivated, so that both men and women have one working X chromosome.

But researchers have recently found that several hundred genes on the X escape inactivation. Taking those genes into account along with the new tally of Y genes gives this result: Men and women differ by 1 to 2 percent of their genomes, Dr. Page said, which is the same as the difference between a man and a male chimpanzee or between a woman and a female chimpanzee.

Almost all male-female differences, whether in cognition, behavior, anatomy or susceptibility to disease, have usually been attributed to the sex hormones. But given the genomic differences that are now apparent, that premise has to be re-examined, in Dr. Page's view.

"We all recite the mantra that we are 99 percent identical and take political comfort in it," Dr. Page said. "But the reality is that the genetic difference between males and females absolutely dwarfs all other differences in the human genome."

Dr. Rice commented that he would have to think through this argument, noting that many genes - up to 15 percent in some animals - are more active in one sex than the other. These differences in gene activity might dwarf the genomic differences described by Dr. Page, he said.

Another difference that has emerged between men and women concerns their ribosomes, the numerous small engines in the cell that build its working parts from the instructions in the genes. A general purpose gene on the Y makes a ribosome component. Its counterpart gene on the X makes a slightly different protein.

That means that every ribosome in a man's body is slightly different from those in a woman's. Though the difference is pervasive, Dr. Page said, it was not known what significance it may have, if any.
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We indeed are wonderfully made!