Sociologists have long recognised that organisations of less than 200 individuals can operate through the free flow of information among the members. Once their size goes beyond this figure, the organizations are getting less flexible. So it seems necessary to prevent total disorder resulting from failures of communication.

One solution to this problem would, of course, be to structure large organisations into smaller units of a size that can act as a group. By allowing these groups to build reliance on each other, larger organizations can be built up. However, merely having groups of, say, 150 will never of itself be a complete solution to the problems of the organization. Something else is needed: the people involved must be able to build direct personal relationships. To allow free flow of information, they have to be able to communicate with each other in a casual way. Maintaining too formal a structure of relationships inevitably prevents the way a system works.

The importance of this was drawn to my attention two years ago by the case of a TV station. Whether by chance or by design, it so happened that there were almost exactly 150 people in the station. The whole process worked very smoothly as an organization for many years until they were moved into purpose-built accommodation. Then, for no apparent reason, the work seemed to be more difficult to do, not to say less satisfying.

It was some time before they work out what the problem was. It turns out that, when the architects were designing the new building, they decided that the coffee room where everyone ate their sandwiches at lunch times was an unnecessary luxury and so did away with it. And with that, they accidentally destroyed the close social networks that strengthened the whole organization. What had apparently been happening was that, as people gathered informally over their sandwiches in the coffee room, useful information was casually being exchanged.

A few years ago, a young woman at Facebook came to my desk and asked if she could speak privately. We headed into a conference room, where she began firing off questions about how I balance work and family. As the questions came faster and faster, I started to wonder about her urgency. I interrupted to ask if she had a child. She said no, but she liked to plan ahead. I inquired if she and her partner were considering having a child. She replied that she did not have a husband, then added with a little laugh, “Actually, I don’t even have a boyfriend.”

It seemed to me that she was jumping the gun but I understood why. From an early age, girls get the message that they will have to choose between succeeding at work and being a good mother. By the time they are in college, women are already thinking about the trade-offs they will make between professional and personal goals! When asked to choose between marriage and career, female college students are twice as likely to choose marriage as their male classmates. And this concern can start even younger. Peggy Orenstein, the author of Cinderella Ate My Daughter, related the story of a five-year-old girl who came home distraught from her after-school program and told her mother that both she and the boy she had a crush on wanted to be astronauts.When her mother asked why that was a problem, the little girl replied, “When we go into space together,who will watch out kids?” At five,she thought the most challenging aspect of space travel would be dependable childcare.

As I’ve mentioned, I’m a big believe in thoughtful preparation. Everywhere I go, I carry a little notebook with my to-do list. But when it comes to integrating career and family, planning too far in advance can close doors rather than open them. I have seen this happen over and over. Women rarely make one big decision to leave the workforce. Instead, they make a lot of small decision along the way, making accommodations and sacrifices that they believe will be required to have a family. Of all the ways women hold themselves back, perhaps the most pervasive is that they leave before they leave.

If you could change your child's DNA in the future to protect them against diseases, would you? It could be possible because of technology known as CRISPR- Cas, or just CRISPR.

CRISPR involves a piece of RNA, a chemical messenger, designed to work on one part of DNA； it also uses an enzyme (If) that can take unwanted genes out and put new ones in, according to The Economist. There are other ways of editing DNA, but CRISPR will do it very simply, quickly, and exactly.

The uses of CRISPR could mean that cures are developed for everything from Alzheimer's to cancer to HIV. By allowing doctors to put just the right cancer-killing genes into a patient's immune system, the technology could help greatly.

In April scientists in China said they had tried using CRISPR to edit the genomes (基因组)of human embryos. Though the embryos would never turn into humans, this was the first time anyone had ever tried to edit DNA from human beings. With this in mind, the US' National Academy of Sciences plans to discuss questions about CRISPR s ethics(伦理问题).For example_? CRISPR doesn't work properly yet. As well as cutting the DNA it is looking for, it often cuts other DNA, too. In addition, we currently seem to have too little understanding of what DNA gives people what qualities.

There are also moral questions around playing God”. Of course, medicine already stops natural things from happening-for example, it saves people from infections. The opportunities to treat diseases make it hard to say we shouldn't keep going.

A harder question is whether it is ever right to edit human germ-line(种系)cells and make changes that are passed on to children. This is banned in 40 countries and restricted in many others. However, CRISPR means that if genes can be edited out, they can also be edited back in. It may be up to us as a society to decide when and where editing the genome is wrong.

Also, according to The Economist, gene editing may mean that parents make choices that are not obviously in the best interests of their children: “Deaf parents may prefer their children to be deaf too； parents might want to make their children more intelligent at all costs.

In the end, more research is still needed to see what we can and can't do with CRISPR. “It's still a huge mystery how we work,” Craig Mello_? a UMass Medical School biologist and Nobel Prize winner, told The Boston Globe, "We're just trying to figure out this amazingly complicated thing we call life.