She Has Her Mother’s Laugh summary

What does a nineteenth-century Moravian monk have to do with the emergence of genetics? Quite a lot, actually.

Gregor Mendel was a young monk of the conservative Augustinian order, teaching math and science at a priory in rural Austria, when he was sent to the University of Vienna for further training. When he returned to the priory in 1853, he continued his scientific education independently.

In the annals of courtroom history, cases of disputed paternity go back a long way. But it wasn’t until the early twentieth century that judges and juries were able to look to biological evidence to settle these cases.

One early, high-profile paternity dispute took place in Hollywood in 1942, when the actress Joan Barry claimed that Charlie Chaplin was the father of her daughter, Carol Ann. She sued him for child support and prenatal costs.

In Georgian London, two people with dwarfism named Judith and Robert Skinner made their living by exhibiting themselves as “curiosities.” They soon earned enough money to retire and start a family. At the time, it was common for people with dwarfism to earn a living like this. What the Skinners did next, though, was less common. Having run out of money, they went on tour again, this time with their children. This second iteration of the Skinner’s exhibition attracted even more public interest. Why? Because the Skinners’ children were all of average height.

Geneticists have long been fascinated by height as an inherited trait. On the one hand, it’s clear to see that tall parents often produce tall children and short parents often produce short offspring. On the other hand, this blueprint doesn’t hold true 100 percent of the time – some children differ wildly in height from their parents. So, what’s going on?

In 1953, a woman known as Mrs. McK went to donate blood. But once scientists analyzed her blood sample, they found something surprising. Mrs. McK had a mixture of type A and type O blood running in her veins. There are four blood types: A, B, AB, and O. Type OA blood was, seemingly, a genetic impossibility.

The scientists concluded that Mrs. McK must have been the recipient of a botched blood transfusion. But Mrs. McK had never had a transfusion.

When does life begin?

Scientifically speaking, it begins with a single-celled zygote, an egg that’s been fertilized by sperm. Inside the zygote, two discrete DNA chromosomes, the molecules that contain all of an organism’s DNA, are mingled and reshuffled. The zygote grows, dividing into two cells, then four, then eight, each imprinted with this new DNA. This collection of ever-multiplying cells becomes an embryo, and then a fetus: a new human life.

Some traits, like eye color, are innate, meaning they are hardwired into our DNA and passed down from one generation to the next. Other traits, conditions, and behaviors – things like depression, or heart disease – can be acquired, meaning we develop them throughout our lifetimes.

But here’s where it gets interesting. Scientists have found that acquired traits, like innate traits, can also be passed down at a genetic level, from one generation to the next.

Did you know that about two-thirds of humans have some form of lactose intolerance? The explanation for this widespread intolerance – and for why the remaining two billion or so people on the planet can enjoy a bowl of ice cream with no nasty side effects – lies in our genetic makeup.

Here’s something weird about humans: we’re the only mammals that consume milk products after we’ve been weaned from our mothers’ breast milk. After they’re weaned, other mammals stop producing lactase, the enzyme that allows them to break down the sugars contained in milk. Without lactase, milk and milk products are difficult to digest.