Imagine that the genome （基因组） is a bookThe book consists of 23 chapters with thousands of

Imagine that the genome （基因组） is a book．The book consists of 23 chapters with thousands of stories made up of paragraphs, words and letters on different levels．There are one billion words in the book, as long as 800 Bibles; if I read the genome out to you at the rate of one word per second for eight hours a day, it would take me centuries; if I wrote out the human genome, one letter per millimeter, my text would be as long as the River Danube．This is a huge volume, a book of great length, but it all fits inside an extremely small cell nuclear（细胞核） that fits easily upon the head of a pin．
The idea of the genome as a book is not, strictly speaking, even a metaphor．It is true to a great extent．A book is a piece of digital information, written in one-directional form and defined by a code that translates a small alphabet of signs into a large dictionary of meanings through the order of their groupings．So is a genome．The only difference is that all English books read from left to right, while some parts of the genome read from left to right while some from right to left, but never both at the same time．
While English books are written in words of different lengthens using twenty-six letters, genomes are written entirely in words of three-letter length, using only four letters, and instead of being written on flat pages, they are written on long chains of DNA molecules （分子）．
The genome is a very clever book, because in the right condition it can both photocopy itself and read itself．
【小题1】How do human genomes read according to the passage? A．Only from left to right．B．Only from right to left．C．From both directions at the same time．D．From one direction at a time．【小题2】We can learn from the passage that the human genome ．A．is as long as the River DanubeB．can be easily placed on the head of a pinC．is coded with an alphabet of four lettersD．is smart enough to read and take photos of itself【小题3】It can be concluded that the passage is mainly written for ．A．specialists in the fieldB．general readersC．natural scientistsD．readers with professional knowledge【小题4】The real purpose of the author’s comparison of the genome to a book is ．A．to focus on the differences between the twoB．to lay emphasis on the similarities between the twoC．to simplify the concept of the human genomeD．to give an exact description of the human genomeD

(答案→)D 解析：文章用比喻的方法讲述了深奥的基因组的理论。【小题1】D 细节题。根据第2段最后三行The only difference is that all English books read from left to right, while some parts of the genome read from left to right while some from right to left, but never both at the same time．可知D正确。【小题2】C 细节题。根据第三段2,3行genomes are written entirely in words of three-letter length, using only four letters可知C正确。【小题3】B 推理题。文章通过形象的比喻，把基因比喻成一本书，以浅显的方式讲述了深奥的理论，说明是讲给一般的读者的，而不是那些专业的认识。故B正确。【小题4】C 推理题。作者把基因比喻成书是为了更简单的讲述这个道理，是深奥的原理简单化。

谢谢了