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  3. What does DNA look like? [originaltext]Deoxyribonucleic acid, DNA for short, is

What does DNA look like? [originaltext]Deoxyribonucleic acid, DNA for short, is

游客2023-12-24  99
问题 What does DNA look like?
Deoxyribonucleic acid, DNA for short, is a molecule composed of two chains that coil around each other to form a double helix carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses.
选项 A、It is a single-strand folded onto itself.
B、It is a paired double-strand spirally shaped.
C、It is made up of two unbent strands connected to each other.
D、It is a molecule carrying genetic information.
答案 B
解析 语义的理解与画面构建。本段介绍的是DNA，包括其形状、功能和存在范围。而该题所问的是“What does DNA look like”，即DNA是什么样子的。因此，首先排除选项D，与所问无关。再根据原文与DNA形状有关的陈述，“a molecule composed of two chains that coil around each other to form a double helix”，可知DNA是双链分子，两条链呈螺旋状连接，形成双螺旋结构。选项A将DNA描述为单链结构（single strand），错误。选项C将DNA描述为直链（unbent），错误。因此，本题应选择选项B。
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