The United States has just over 300 million people. If you break that down to a biological level, that equals about 13.8 billion human chromosomes, and at least 90 trillion human genes. So what do all these genes say about the country? What do they say about us? In his new book "DNA USA: A Genetic Portrait of America," Bryan Sykes tackles this issue head-on.

One in eight people over age 65 suffers from Alzheimer's disease. Most patients develop late-onset Alzheimer's. Scientists have found a predisposing genetic risk factor for this type of the disease, and while they have yet to discover a direct genetic link, researchers have isolated the early-onset Alzheimer’s gene. Early-onset Alzheimer's is rare, affecting only five percent of Alzheimer’s patients. But it can strike as early as 30, with devastating consequences for the patient and their families. Many families are unprepared for the difficult decisions caregivers face when their loved ones are diagnosed with early- or late-onset Alzheimer's. 

What tendencies are we born with? What is a choice? And does it make you feel better or worse to know that certain things – ranging from weight to our intelligence — are one or the other?

Think, for example of sexual orientation. A lot of people have a lot invested in whether we’re born gay or whether it’s a choice. Is it one or the other? Does it even matter?

We look ahead at this week in news. It's the official beginning of shrimping season in Louisiana; Russia's grain embargo has just taken effect; the Obama administration tries to figure out how to approach mortgage giants Fannie Mae and Freddie Mac; a judge's ruling effectively bans planting genetically modified sugar beets; and the Congressional Budget Office will release its budget outlook.

A team of scientists have successfully developed new living bacteria from non-living parts, which they’re calling the first “synthetic cell.”

In a newly-released paper in the journal Forensic Science International: Genetics, scientists in Tel Aviv, Israel, describe how they have found a process to fabricate DNA. The process involved removing DNA from a woman’s blood sample and adding DNA from a different person. The process was so easy, they say, that any biology undergraduate has the tools to engineer his or her own crime scene.  (DNA evidence left at crime scenes has been considered nearly incontrovertible in the past; this process raises questions about its reliability going forward.) 

We talk to Timothy Bestor, a professor of genetics and development at the College of Physicians and Surgeons of Columbia University, and Tania Simoncelli, a science advisor at the American Civil Liberties Union.

Anyone who has watched wildlife documentaries may know that animal behavioral patterns are tracked by inserting microchips into the animals' bodies. This is tricky, because it requires tranquilizing the animal in order to place the chip. But new technology now allows for non-invasive research. Science journalist Jim Robbins joins The Takeaway to explain how scientists are using technology and animal products, like poop, to learn everything they can about wildlife without even touching the animals.

For more, read Jim's piece on DNA-powered wildlife research in the New York Times article, Tools That Leave Wildlife Unbothered Widen Research Horizons.

If you want to do your own wildlife surveys, you'll need to be able to match scat with the critter that created it. To bone up, watch this video.

It doesn't sound nonsensical to say that what happens when we are younger stays with us the rest of our lives. But today, for the first time ever, scientists reveal that childhood abuse can affect our genes by altering the biology of our brains. Luckily these markers can be wiped clean in the next generation and the cycle can end. In this segment, John Hockenberry goes knee-deep into the brain with guest Michael Meaney, one of the lead researchers on the work, which appears online in the journal Nature Neuroscience.

For more, read the very scientifically written and deeply wonky article abstract, Epigenetic regulation of the glucocorticoid receptor in human brain associates with childhood abuse.

Have more questions? Michael Meaney is happy to answer your questions. Post here and he'll respond.