How can different cells do different jobs in the human body with the same DNA

Almost all of the cells in your body share the same DNA as was found in that first cell. For a cell to work, 1000's of these proteins must be made, each doing its particular job. Eyes and lungs are so different because different sets of proteins are made in the various eye and lung cells.

Explanation:

Almost all of the cells in your body share the same DNA as was found in that first cell*.  For a cell to work, 1000's of these proteins must be made, each doing its particular job. Eyes and lungs are so different because different sets of proteins are made in the various eye and lung cells.

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