"Over the years the unthinkable hasbecome thinkable and today we sense we are close to being able to alter humanheredity œ#)." These were the words of David Baltimore of the CaliforniaInstitute of Technology, on December 1st, when he opened a three-day meeting inWashington to discuss the morality and use of human gene editing. Dr Baltimoreis an old hand at these sorts of discussions, for he was also a participant inthe Asilomar conference, in 1975, which brought scientists together to discussa safe way of using the then-new tcchnology of recombinant DNA, and whoserecommendations influenced a generation of biotechnology researchers.

Four decades on, the need for a similarsort of chin-wag has arisen. The InternationalSummit on Human Gene Editing has been held by the national scientific academiesof three countries — America, Britain and China. They are particularlyconcerned about whether gene editing should be used to make heritable changesto the human germ line, something Dr Baltimore described as a deep andtroubling question. Like those of Asilomar, the conclusions of this meetingwill not be binding. But the hope is that, again like Asilomar, a mixture ofcommon sense and peer pressure will create a world in which scientists aretrusted to regulate themselves, rather than having politicians and civilservants do it for them. The meeting is being held against a backdrop of rapidscientific advance, Since 2012 research into a new, easy-to-use editing tool calledCRISPR-Cas9 has blossomed. This technique involves a piece of RNA (a chemicalmessenger, which can be used to recognise a target section of DNA) and anenzyme (酶)called a nuclease that can snip unwanted genes out and paste new ones in.

Public interest was aroused in April,when Chinese scientists announced they had edited genes in non-viable ( 无活力的) humanembryos, and again in November when British researchers said they hadsuccessfully treated a one-year-old girl who had leukaemia ( 白血病),using gene-edited T-cells. T-cells are part of the immune system that attack,among other things, tumour cells. The researchers altered T-cells from ahealthy donor to encourage them to recognise and kill the patient's cancer, tomake them immune to her leukaemia drug, and to ensure they did not attack herhealthy cells.

In another recent development, a firmcalled Edit as Medicine, which is based in Cambridge, Massachusetts, has saidit hopes, in 2017, to start human clinical trials of CRISPR-Cas9 as a treatmentfor a rare genetic form of blindness known as Leber congenital amaurosis (伯氏先天性黑蒙).Though other companies are already testing gene-editing therapies, these employolder, clunkier forms of the technology that seem likely to have lesscommercial potential. Moreover, researchers at the Broad Institute, also inCambridge, said this week that they had made changes to CRISPR-Cas9 whichgreatly reduce the rate of editing errors — one of the main obstacles to thetechnique's medical use.

On the subject of germ-line editing,Eric Lander, the Broad's head, told the meeting it would be useful only in rarecases and said it might be a good idea to "exercise caution? before makingpermanent changes to the gene pool. The need for caution is advice that mightalso be heeded by those pursuing work in animals other than people, and inplants — subjects not being covered by the summit.

    One of the most exciting and interesting international cities to visit is London, England. Here is a look at four free things to do during a vacation to London.

    Visit the Trafalgar Square

    Built more than 200 years ago, Trafalgar Square is a popular gathering place for locals and travelers, too. The area is close to good shopping and dining opportunities, and there are usually some sorts of public events or celebrations going on there during most weekends.

    Wander Along the Thames

    Visitors wanting to sec some great architecture, attractions and views should spend an afternoon walking along the River Thames. The best place to start is at the world-famous London Bridge crossing over the river and you can walk all the way to Westminster Bridge a short distance away. Travelers doing this will find themselves passing by a great many historic buildings.

    Explore the Local Markets

    While purchasing items at any of the open markets in London is not necessarily free, walking through them to view the merchants（商人）, their products and the other shoppers is of great fun. Some of the popular open markets in London worth visiting include Spitafields Market, Portobello Road Market and Leadenhall Market.

     Visit the British Museum

    One of the top museums in the entire United Kingdom can be found in London, and it charges no admission（人场费）for entry. This museum is so highly regarded that it is not only popular with locals and tourists, it is also seen as a major and valuable scholarly resource.

    Philadelphia offers a ton of attractions that are suitable for people of every age and here are some family—friendly attractions.

    Spruce Street Harbor Park

    Spruce Street Harbor Park, one of the best urban beaches in American, is an outdoor heaven on the Delaware River waterfront. Visitors can relax in a hammock, play on the playgrounds, and play games like table tennis and giant chess. Don't miss out on the park at night, when colorful LED lights hanging from treetops make the entire area bright.

    Blue Cross RiverRink

    Offering ice skating in the winter and roller skating in the summer, Blue Cross RiverRink creates a fun，outdoor experience for the whole family. Visitors can play on the nine-hole mini-golf course during the summer, and enjoy eats and drinks from the on-site (现场的) bar and restaurant all year round.

    Sesame Place

    Big Bird, Elmo and the other stars of Sesame Street come out and play at Sesame Place, the only theme park in the nation starring the popular TV show's most lovable characters. A water park, interactive activities，parades, fireworks and shows add to the fun.

    Once Upon a Nation Storytelling Benches

    On summer days, uniformed and professional storytellers at 13 storytelling benches throughout Philadelphia's Historic District entertain visitors with true, free, three-to-five minute tales about the colonial (殖民的）era as part of Once Upon a Nation . Children can pick up a Story Flag at any storytelling bench, and then collect a star from every storyteller on their journeys. Flags with all the stars can get free rides on the Parx Liberty Carousel at Franklin Square.

    It was when I was walking to my office, trailed by three young people whose ages ranged from 16 to 25, flowing down the corridor behind me like the tail of a kite, that I thought of it for the first time.

    This could be because I am not actually a mother. Until recently, I was not a "real" stepmother either. But I have been living with the man who is now my husband, Bernardo for 10 years and in those 10 years, not only have his younger daughters spent every other weekend and half of their school holiday with us but also his son has lived with us full-time. In fact, when Bernardo asked me to move in, he asked his son for permission first.

    Being a step mum is hard enough but being a sort-of-step-mother is about the most awkward position a mature woman can find herself in. With my sort-of-steppies, I have occupied a place of influence, power and sometimes extreme anger by turns. I have stepped on a delicate path between being a grown-up friend, a bridge of influence with their father, the woman of the house, and a figure of authority – but not too much.

    Love the kids or hate them, you must always remember that no matter how much you cook, clean, hug, comfort and discipline, you will never actually count.

    To survive, I trained myself to love the stepkids as hard as I could, but not to care. It's a handy piece of good mental health trickery I recommend to anyone in my position. I can help with homework, yes, but not bother about the results of that homework. I can teach them good manners, but not care about the bad habits they learn at home. Semi-detached is the position.

    Closeness and independence are both important in our life. Though all humans need both of them, women tend to focus on the first and men on the second. It is as if their lifeblood ran in different directions.

    These differences can give women and men differing views of the same situation, as they did in the case of couple I will call Tracy and Brian. When Brian's old high school friend called him at work and announced he'd be in town on business the following month, Brian invited him to stay for the weekend. That evening he informed Tracy that they were going to have a houseguest, and that he and his friend would go out together the first night to chat like old times. Tracy was upset. She was going to be away on business the week before, and the Friday night when Brian would be out with his friend would be her first night home. But what upset her the most was that Brian had made these plans on his own and informed her of them, rather then discussing them with her before extending the invitation.

    Tracy would never make plans, for a weekend or an evening, without first checking with Brian. She can't understand why he doesn't show her the same courtesy and consideration that she shows him. But when she protests, Brian says, "I can't say to my friend, 'I have to ask my wife for permission'!"

    To Brian, checking with his wife means seeking permission, which implies that he is not independent, not free to act on his own. To Tracy, checking with her husband makes her feel good to know and show that she is involved with someone, that her life is bound up with someone else's.

    Tracy and Brian both felt upset by this incident because it cut to the core of their primary concerns. Tracy was hurt because she sensed a failure of closeness in their relationship: He didn't care about her as much as she cared about him. And he was hurt because he felt she was trying to control him and limit his freedom.

    It's a common belief that the roles actors play might somehow reflect their true personalities. It's usually not true, but British actress Phoebe Waller-Bridge, 34, is an exception.

    Just like Fleabag, the character she played in the comedy-drama series of the same name, Waller-Bridge feels that her life is a mess. "It's just really wonderful to know that a dirty and messed up woman can make it to the Emmys," she said. She may be "messed up", but Variety magazine calls her an "all-around icon".

    Last month, Waller-Bridge took home three Emmy awards for her work on Fleabag — best writing in a comedy series, best lead actress, and best comedy series.

    Her success is partly because of her family. Waller-Bridge was brought up in a free environment. Her mother always told her, "You can be whatever you want if you imagine it." So Waller-Bridge broke all the rules about what a "good" girl should do. "Our laws and moral codes don't apply — she lives without fear of consequence," The Sun noted.

    That fearlessness extends to being authentic (真实的) in her writing and acting. Unlike the can-do heroines and strong, successful women in many TV dramas, Waller-Bridge shows a flawed but real character. The character Fleabag was a screw-up who always found a way to say or do the wrong thing. "It resonated with the lives of stressed-out women everywhere in reality — doing their best to find balance in their lives," a viewer wrote on US movie website.

    Villanelle in Killing Eve, another hit TV series developed by Waller-Bridge, was a little bit violent but showed no interest for the rules others created, which make many people see themselves in her.

    "People have been scared to write characters like these. But I think, now, women are so relieved to have this new template (样板). And, aren't we all a bit of everything?" Waller-Bridge said in an interview with Indian Express.

    With such courage and sincerity, Waller-Bridge is, without a doubt, a "golden girl" in Hollywood, Australian news website The New Daily commented.