HARI SREENIVASAN: The people around the Dallas-Fort worth, Texas, region took stock of tornado damage today and counted their blessings.
A barrage of tornadoes yesterday damaged or destroyed 650 homes, but there were no deaths and only a few serious injuries.
The wrath of one of Tuesday's tornadoes was clearly visible today in Forney, Texas. But as bad as it was, the city's mayor acknowledged it could have been much worse.
DARREN ROZELL, mayor of Forney, Texas: It's difficult to look at the damage to the homes and look around the town and call this a situation where we're blessed. But if you really think about it, the fact that everybody that woke up in Forney yesterday morning is still alive today in Forney, that's a real blessing.
HARI SREENIVASAN: More than 70 homes in Forney were damaged or destroyed by two twisters that ripped through the town.
MAN: Oh, wow! Power flashes. Oh, my goodness.
HARI SREENIVASAN: This enormous funnel cloud ripped through Lancaster with winds up to 165 miles an hour. The Red Cross estimated 40 homes were damaged there.
WOMAN: Amazing that we're still living. Terrible.
HARI SREENIVASAN: A news helicopter captured another twister's fury as it touched down near Arlington.
MAN: Look, look, look, these huge trailers, these huge rigs, the back ends of tractor that are literally being picked up and thrown hundreds of yards.
HARI SREENIVASAN: The storms knocked out power for thousands. In Arlington, 14,000 residents were still in the dark today. And about 1,400 people slept at Dallas-Fort Worth International Airport. The storms canceled hundreds of flights Tuesday and that, in turn, snarled schedules today, with another 500 flights scrubbed.
In all, the National Weather Service said as many as a dozen twisters touched down in North Texas.
Wall Street had one of its worst days in a year. A lackluster bond auction in Spain revived concerns about Europe's debt problems, and that set off a wave of selling. The Dow Jones industrial average lost nearly 125 points to close at 13,074. The Nasdaq fell 45 points to close at 3,068.
The president signed a bill today that bars members of Congress from using inside information to profit on the stock market. The new Stock Act also affects the president himself and thousands of federal employees. Mr. Obama said the statute would ensure that everyone plays by the same rules.
Internet giant Yahoo will lay off 2,000 employees, about 14 percent of its work force. The announcement today was part of the company's plans to redeploy resources and boost revenues. Yahoo estimated it will save $375 million a year from the cuts. This is the sixth, and largest, mass layoff for Yahoo in four years.
In Afghanistan, three American soldiers were killed in a suicide bombing in the north. Seven Afghans died as well, and at least 20 people were wounded. It happened in the capital of Faryab province. Onlookers and troops viewed the carnage after the bomber rode up on a motorcycle and triggered his explosives.
A top militant leader in Pakistan was defiant today after the U.S. offered a $10 million bounty for his arrest. Hafiz Muhammad Saeed founded the group Lashkar-e-Taiba. He's been accused of orchestrating the 2008 bombings in Mumbai, India, that killed 166 people, including six Americans.
He appeared at a news conference today in Rawalpindi, Pakistan and mocked the U.S. bounty.
HAFIZ MUHAMMAD SAEED, Pakistani militant leader (through translator): To be honest, I am surprised that America doesn't know where I am. These threats, putting money on my head to help my arrest, are for people hiding in mountains and caves, and no one knows about them. But, with the grace of God, I am here in front of you people, and tomorrow I will be in Lahore and will release a schedule for the day after tomorrow, so America can contact me whenever it wants to.
HARI SREENIVASAN: In Washington, State Department spokesman Mark Toner said finding Saeed is not the issue. He said the bounty is for information that will bring a conviction.
MARK TONER, State Department spokesman: So I think what's important here is we're not seeking this guy's location. We all know where he is. Every journalist in Pakistan and in the region knows how to find him. But we're looking for information that can be usable to convict him in a court of law.
HARI SREENIVASAN: The government of Pakistan said today the U.S. must provide concrete evidence if it wants action against Saeed.
The military trial of the alleged 9/11 mastermind will resume soon at Guantanamo Bay. Khalid Sheikh Mohammed's trial was put on hold two years ago when President Obama tried to transfer it to a civilian court. Congress blocked that effort, and today, military officials set an arraignment in May. Mohammed and four others are charged with terrorism and murder.
Five former police officers in New Orleans were sentenced to prison today in the shootings of unarmed civilians during Hurricane Katrina. The sentences ranged from six to 65 years on federal civil rights and firearms charges. Two people were killed, and four more wounded in the shootings on New Orleans' Danziger Bridge.
New research has shed light on genetic changes that raise the risk of autism. The journal Nature published the results of three studies today involving hundreds of families with autistic children. The studies showed that spontaneous mutations can increase the chances of autism. And fathers are four times more likely to pass on the mutations.
Dr. Thomas Insel is director of the National Institute of Mental Health, which helped fund the studies. I spoke with him earlier.
Dr. Insel, thanks for being with us. Help us understand what a spontaneous mutation is. We have millions of these happening already, right? Why is this connected to autism?
DR. THOMAS INSEL, director, National Institute of Mental Health: Well, we all have changes in our genomes that, amazingly, weren't present in either our moms or dads. These are spontaneous. And they occur perhaps at random.
We don't actually know entirely how they occur, but all of us have them. One possibility here is that those people who have autism have random mutations like this, spontaneous, that are occurring in just the wrong part of the genome, affecting genes that you need for neurodevelopment.
HARI SREENIVASAN: What about the correlation between aging fathers and autism? What do these studies reveal there?
DR. THOMAS INSEL: Well, these studies suggest that the risk is somewhat higher in dads over 40. Now, we have known that for some time that especially dads over 40, boys with autism are about six-fold more likely to have a father over 40, girls with autism about 17-fold more likely to have a father over 40.
But let's be clear that that's a very small part of the risk for autism that contributes, but contributes in a very minor way.
HARI SREENIVASAN: So there's always been a raging debate in the autism community on whether it's a genetic cause or whether it's an environmental cause. What do these studies -- do they shed light on either of those?
DR. THOMAS INSEL: Well, I think they do.
I mean the reality here is that some autism is truly genetic and it's certainly likely that some autism is going to be more due to environmental causes. What these new studies suggest is that the two may really fit together, that the environment may be affecting the risk for autism by influencing the genome itself and actually increasing the likelihood of these spontaneous mutations.
HARI SREENIVASAN: All right, Dr. Thomas Insel, director of the National Institute for Mental Health, thanks so much for your time.
DR. THOMAS INSEL: Thank you.
HARI SREENIVASAN: Baylor University took the NCAA women's basketball championship last night and made history in the process. The Lady Bears' 80-61 victory over Notre Dame completed a perfect season and gave them 40 wins. It's the first time a college team of either gender has won that many games in one season.
Those are some of the day's major stories.