Study: 'Male' chromosome to stick around

[Sean]

http://edition.cnn.com/2005/TECH/sci....ap/index.html

NEW YORK (AP) -- The human Y chromosome -- the DNA chunk that makes a man a man -- has lost so many genes over evolutionary time that some scientists have suspected it might disappear in 10 million years. But a new study says it will stick around. Researchers found no sign of gene loss over the past 6 million years, suggesting the chromosome is "doing a pretty good job of maintaining itself," said researcher David Page of the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts. That agrees with prior mathematical calculations that suggested the rate of gene loss would slow as the chromosome evolved, Page and study co-authors note in Thursday's issue of the journal Nature. And, they say, it clashes with what Page called the "imminent demise" idea that says the Y chromosome is doomed to extinction. The Y appeared 300 million years ago and has since eroded into a dinky chromosome, because it lacks the mechanism other chromosomes have to get rid of damaged DNA. So mutations have disabled hundreds of its original genes, causing them to be shed as useless. The Y now contains only 27 genes or families of virtually identical genes. In 2003, Page reported that the modern-day Y has an unusual mechanism to fix about half of its genes and protect them from disappearing. But he said some scientists disagreed with his conclusion. The new paper focuses on a region of the Y chromosome where genes cannot be fixed that way. Researchers compared the human and chimpanzee versions of this region. Humans and chimps have been evolving separately for about 6 million years, so scientists reasoned that the comparisons would reveal genes that have become disabled in one species or the other during that time. They found five such genes on the chimp chromosome but none on the human chromosome, an imbalance Page called surprising. "It looks like there has been little if any gene loss in our own species lineage in the last 6 million years," Page said.

Thought it was interesting and the Science forum could always use a boost in topics

[Protostar]

Quote by: Sean http://edition.cnn.com/2005/TECH/sci....ap/index.html Thought it was interesting and the Science forum could always use a boost in topics

So, what does that mean, that we are evenually going all turn into females?

[Compugasm]

No, that we will all turn into reptiles. There will be nothing "human" at all without that gene.

[Jack]

WooHoo, reverse evolution. It's about time.

So, what does that mean, that we are evenually going all turn into females?

No, just some of us.
Actually, if you'll note this sentence;

Researchers found no sign of gene loss over the past 6 million years, suggesting the chromosome is "doing a pretty good job of maintaining itself,"

you'll see you don't have anything to worry about, at least for the next few thousand years.

[SteveA]

Sexual reproduction has an advantage over asexual reproduction. With sexual reproduction, offspring inherit a variety of genes from both parents and are more diverse. This provides protection against threats that would otherwise destroy a population of relatively identical genetic makeup.

Asexual reproduction is simple, and it's easier for asexual animals to spread to remote locations because they don't need to find/bring a partner to reproduce, but the weakness of having all the children be effectively clones of the parent with no new genetic input leaves the entire population susceptible to preditors or or diseases that take advantage of whatever weaknesses are present.

A couple other thoughts I've had along these lines are:

1) If X chromosomes contain the majority of expressed genetic information versus the Y chromosome, then it would seem that women must have a lot of repressed genetic information, while men are more of an expression of a single chromosome. In nature, selective pressures seem to be placed more on males, which would partly due to the fact that they don't spend as much energy on having offspring, but also this could be due to the fact that they are more representative of a single chromosome and so selective forces on males correlate closer to evaluating a chromosome, which is likely more accurate.

2) It's possible much of the random and repetitive information in the Y chromosome is simply a random "soup" to provide a greater variety or bias in genetic makeup of the offspring. I'm more familiar with genetic algorithms in engineering than in biological genetics, and don't know to what extent that's physically possible, but nature has continually seemed to demonstrate the efficiency of organisms and I wouldn't be surprised if what appeared relatively random or repetitive was simply due to our inability to interprete the effects.

3) For humans and other complex animals that have a long time in development before they are independent adults, it can be a benefit to have two parents. If resources are scarce or the death of a single parent likely, having two parents increases the survivability of the offspring and can increase their learning as well. One parent can forage while the other babysit, as often occurs.

(Now here's a question - when will we see a Z chromosome? )