题干

下图为人类某种单基因遗传病系谱图,II4为患者,则下列相关叙述合理的是(   )

A:该病一定属于常染色体隐性遗传病

B:II3是携带者的概率为1/2

C:若I2不携带致病基因,则I1的一个初级卵母细胞中含有2个致病基因

D:若I2携带致病基因,则I1和I2再生一个患病男孩的概率为1/4

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C

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Why I've taken a break from holidays

    It is now close to four years since I last took a holiday. This is because I have come to the conclusion, over the course of my adult life, that I am not very good at it. You might think this sounds like saying you're not very good at drinking tea or listening to music. What could possibly be difficult about the natural act of putting your working life on hold for a couple of weeks and going somewhere warm to do nothing?

    I was a model holidaymaker as a kid. However, the problems started during my twenties. A trip to the south of France was ended after just two days, mainly because I had an urge to check my e-mails. Similarly, my honeymoon was cut short by 48 hours—not because my wife and I weren't enjoying ourselves, but because we were missing our cats.

    So what is my problem? On the surface, I'm probably a bit of a homebody. And I just find the pressure of being on holiday too severe: it always feels like having a gun held to my head and being forced to have fun. Somehow, packing a list of possessions and meeting a scheduled flight has none of the excitement of suddenly deciding to take a day off and driving somewhere for the fun of it.

    Thankfully, I'm not alone. This summer, most of my friends have decided not to have a break. And a recent survey (调查) proved the downside of holidays, with the results showing that nearly two thirds of people found that the calming effects of a holiday wore off within 24 hours, as stress levels returned to normal. And this year The Idler magazine published its Book of Awful Holidays. Here you will find a list of the five most ecologically-damaging vacations it's possible to take, along with 50 painful holiday experiences voted for on The Idler website.

    What interests me is what the concept of a “holiday” says about our lives. For me, the point of living is to have a life you enjoy for 52 weeks a year. The more I like my life and the better I structure it, the less I want to go away. Maybe I'm an unusual person for not liking holidays, but I just feel the time when I'm not working is too valuable to waste on them.