The following passage contains ten errors .Each line contains a maximum of one error. In each case only one word is involved. You should proofread the passage and correct it in the following way:
For a wrong word: underline the wrong word and write the correct one in the blank provided at the end of the line.
For a missing word: mark the position of the missing word with a "^" sign and write the word you believe to be missing in the blank provided at the end of the line.
For an unnecessary word: cross the unnecessary word with a slash "/" and put the word in the blank provided at the end of the line.

One important outcome of the work on the expression of genes in developing embryos is sure to be knowledge that can help preventing birth defects. Just as promising
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is the possibility of unraveling the complicated writing
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of the brain. A mechanic gets valuable insight how an
(28)
automobile works by rebuilding car engines; similarly,
neuroscientists can learn how the brain functions from
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the way it is put together. The next step pursuing the
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goal is to find out how the blueprint genes, the home box
genes, control the expression of other genes that create the
valves and piston of the working cerebral engine. The
protein encoded by the latter genes could change the
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stickiness of the cell surface, the shape of the cell or its
metabolism to create the characteristic peculiar to, say,
neurons or neural-crest cell. Surface proteins may be the
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mechanism, whereby similar programmed cells stick
together to form specific structures; they might also sense
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the local environment to help the cell decide what is to do.
Clarifying those mechanisms will engage the best talents in
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embryology and molecular biology for some times to come.
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What is perhaps the most intriguing question of all is if the
brain is powerful enough to solve the puzzle of its own creation.