• 难度: 使用次数:26 入库时间:2017-10-21

        Most people are born with straight hair, but why are there people born with curly hair? It may look like a simple question that we can easily answer, but the answer is not as simple as it seems.

        The colour and shape of your hair are decided by your genes(基因). Whether you have straight hair or curly hair comes from your parents' genes. "If both your parents give you the curly version(版本) of the gene, you end up with curly hair, " Barry Starr, a geneticist at Stanford University, US, told Popular Science. If both give you the straight version you end up with straight hair. And if one gives you curly genes and the other straight, you could end up with either.  But how does DNA work on a single hair?

        Scientists show that the curls of hair depend on the nature of its follicle(毛囊). When a follicle is asymmetrical(不对称的), the hair that it produces is curl. Another point is that the follicle of curly hair has a hooked(钩状的) end. The more hooked the follicle is, the curlier the hair is. Follicles for straight hair have no hooks.

        But even if you are born with straight hair, there are some ways that straight hair can turn curly. Scientists have found that a cell(细胞) called EGFR in follicles appears to control the growth of hair. For example, certain cancer medicine that stop these cells may cause a patient to develop curly hair as a side effect.

    (    )1. The number of people born with curly hair is___ that of people born with straight hair.

             A. larger than                         B. smaller than

             C. twice as large as                 D. as big as

    (    )2. From Paragraph 2, we can know that ________.

             A. our genes can decide the length of our hair

             B. our parents' genes decide whether we have straight or curly hair

             C. Barry Starr is a geneticist from Popular Science

             D. If one boy's parents have straight hair, he may have curly hair

    (    )3. Which of the following statements is TRUE according to Paragraph 3?

             A The nature of hair's cells decides the curls of hair.

             B. If a follicle is asymmetrical, the hair produced is straight.

             C. If follicles for a girl's hair have no hooks, she may have curly hair.

             D. If follicles for a girl's hair have more hooked ends, she has curlier hair.

    (    )4. The passage is possibly from_______.

             A a novel                                    B. a poem

             C. a science book                    D. a news report

    答案

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    1B 2B 3D 4C



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