AAAS Project 2061 Biology Textbooks Evaluation

Will Biology Textbooks Help Students Understand the Science and Implications of the Human Genome Project?

The importance of having mapped the human genome is looming pretty large currently. How will students understand its significance?

Not very well, according to the findings of an evaluation of high school biology textbooks conducted by Project 2061 of the American Association for the Advancement of Science. In the typical textbook, information about the molecular basis of heredity is presented piecemeal:

  • DNA is described in great detail (including the 4 kinds of nucleotides that compose it, how they pair, and how DNA is duplicated),
  • the steps of transcribing DNA through RNA are shown (using terms like replication, complementary bases, and sometimes even replication fork and enzymes DNA polymerase and helicase),
  • RNA is shown (in complicated diagrams) to direct the synthesis of proteins (using terms like mRNA, tRNA, codon, anticodon), and
  • proteins are shown to catalyze other molecular interactions (in an earlier chapter).
  • Changes in genes and their consequences are described (but in a later chapter after presenting Mendel's experiments with garden peas, complete with Punnett squares).

Seldom are these ideas tied together to convey a coherent story.

The coherent basic story that reviewers looked for is shown in the attached map:

  • DNA molecules are long chains linking just four kinds of smaller molecules (nucleotides) whose precise sequence encodes hereditary information.
  • The sequence in a cell's DNA provides instructions for assembling proteins, which carry out most of the work of cells.
  • Changing even a tiny portion of the DNA can change the protein that is produced.
  • Such a change may not make much difference in the operation of the cell, or may change its operation significantly, or even fatally disrupt it.

Because the genome is a map of the sequence of the billions of nucleotides in human DNA, its importance is obvious for understanding cell functions--and dysfunctions. The sequence specifies the complete genetic code, which can be normal or faulty. This code can eventually be deciphered into the proteins (normal or faulty) that make cells function (or dysfunction). Thus the importance of deciphering the human genome can lead to detection of defective genes and, ultimately, to their repair.

But the textbooks' piecemeal treatment of the topic either leaves out the simple story or obscures it in needless details. Unfortunately, the details are easy to give tests on and will often be substituted for a coherent picture that most students will never learn. Since the unconnected details are difficult to remember, students may be left with virtually nothing after a biology course. (Once the basic fundamental story is laid out, details of the stages of RNA transcription and ribosome operation can be learned later by science-specializing students). In evaluating materials, we are looking for signs of a coherent, comprehensible, and memorable foundation for further learning.

Continued: Key Ideas Used for the Evaluation