Tuesday, August 04, 2009

Thinking about textbooks

In preparation for this morning's meeting of the genetics-revision committee, each committee member has reviewed one of the candidate textbooks. I had prepared a checklist of content and presentation issues to guide this, but it was a quick-and-dirty list and I now realize that I overlooked some big issues.

I realized this because I spent yesterday afternoon reviewing the textbook I'd taken on, and yesterday evening reviewing the first (draft) chapter of a new genetics textbook. I filled in my checklist for the former, and sent the publisher a lot of detailed comments on the latter, but now I think I need to add to my checklist and send a second email clarifying the big issues.

One is the difference between information and science. I really like the first-year textbook I've been using (Scott Freeman's Biological Science) because of its explicitly scientific approach. Each topic is introduced as questions: What do we (students and researchers) want to understand? What are the hypotheses? How have they been/are they being tested? Neither genetics textbook I reviewed does this. Instead they present lots of information, but as facts and history, not science.

The history aspect is a big problem. Classic experiments are described in detail, but it's not at all clear why students should know these. The strongest original evidence that DNA carries genetic information came from two now-famous studies. Both textbooks explain these well, but doing so requires explaining a lot of technical details about the experimental systems used (pathogenic bacteria and bacterial viruses) that does nothing to advance students understanding of DNA's function. If we just wanted to convince students that DNA does carry the genetic information, there are many simpler experiments available now, such as transforming bacteria with a plasmid carrying an antibiotic resistance gene. If we want students to learn history, we need to know why.

Another problem is telling the students why particular information is being presented, how they are expected to use what's in the chapter. The draft first chapter I read was densely packed with information on an enormous range of topics: the history of genetics, the structure of DNA, how gene expression works and how it is regulated, how evolution happens, the first organisms, how evolutionary relationships are inferred from DNA sequences. The authors' Prospectus indicated that they think students will already know a fair bit of this, but the students aren't told how they should use this information. Is it meant to be a review? Will they need to know this in order to understand the following chapters?

The techniques students are taught are strangely archaic. Nobody does Southern blots any more, or scores restriction-fragment-length polymorphisms! Instead, modern genetic analysis is based on direct determination of DNA sequences. The technologies that do this are complex, but analysis using sequences is (should be) much more intuitive for students to understand than the indirect methods we used to rely on. I can appreciate how an old textbook such as IGA might be conservative in the methods it describes (laziness, partly, and lack of imagination) but this is inexcusable in a completely new book.

1 comment:

PonderingFool said...

Nobody does Southern blots any more
I know people who do them when constructing knockouts to make sure the gene they are knocking out hasn't migrated somewhere else in the genome. They also do this when making markerless deletions and are screening. Selection is not always possible. Cheaper still to screen via Southern and then sequence the positives than to sequence them all.