题干

着色性干皮症是一种常染色体隐性遗传病,起因于DNA损伤。深入研究发现患者体内缺乏DNA修复酶,DNA损伤后不能修补从而引起突变。这说明一些基因可以

C:控制酶的合成来控制代谢过程,从而控制生物的性状

A:控制蛋白质的合成,从而直接控制生物性状

B:控制蛋白质分子结构,从而直接控制生物性状

D:直接控制生物性状,发生突变后生物的性状随之改变

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C

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    Each time I see a balloon, my mind flies back to a memory of when I was a six-year-old girl. It was a rainy Sunday and my father had recently died. I asked my mom if Dad had gone to heaven. "Yes, honey. Of course." she said.

    "Can we write him a letter?"

    She paused, the longest pause of my short life, and answered, "Yes."

    My heart jumped. "How? Does the mailman go there?" I asked.

    "No, but I have an idea." Mom drove to a party store and returned with a red balloon. I asked her what it was for.

    "Just wait, honey. You'll see." Mom told me to write my letter. Eagerly, I got my favorite pen, and poured out my six-year-old heart in the form of blue ink. I wrote about my day, what I learned at school, how Mom was doing, and even about what happened in a story I had read. For a few minutes it was as if Dad were still alive. I gave the letter to Mom. She read it over, and a smile crossed her face.

    She made a hole in the corner of the letter where she looped the balloon string. We went outside and she gave me the balloon. It was still raining.

    "Okay, on the count of three, let go. One, two, three."

    The balloon, carrying my letter, darted upward against the rain. We watched until it was swallowed by the mass of clouds.

    Later I realized, like the balloon, that Dad had never let his sickness get him down. He was strong. No matter what he suffered, he'd persevere, hang on, and finally transcend this cold world and his sick body. He rose into sky and became something beautiful. I watched until the balloon disappeared into the gray and white and I prayed that his strength was hereditary. I prayed to be a balloon.