<\/a>Introductory biology can be overwhelming; what we consider to be ‘essential foundation’ could take up an entire undergraduate education. This issue is compounded when we treat the body of knowledge as a collection of names and facts (or when students achieve this view despite our efforts). By viewing the cell as a functioning machine, divided into compartments filled\u00a0tasks performed by mindless but efficient mechanisms, a course can focus on\u00a0understanding. A natural framework for student study and learning arises: the mechanics of the cell<\/p>\n

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While Scott Freeman’s ‘Biological Science’ has been\u00a0my choice as textbook for my own Intro Bio course, some of its interesting decisions seem off base to me. The pre-printed highlighting of the text is itself a philosophy of learning. In looking at it, my summary would be “Learn the words and definitions; the sense will take care of itself.” I believe this to be the opposite of the case, and I think current thinking about how people learn<\/a>\u00a0backs this up.<\/p>\n

Instead of approaching Introductory Biology as a body of information, I think good course design would have\u00a0us dividing and conquering the mechanics of the cell into functional, purpose-fulfilling units. This view is one that students are already familiar with from their own lives, and\u00a0thus\u00a0parallels their world. It also demystifies many of the events and processes. As laid out in previous posts, I think most of life’s\u00a0molecules are comprehensible to students and can be better approached\u00a0and better retained<\/em> if we talk about\u00a0how \u00a0<\/em>things work and\u00a0 why \u00a0<\/em>they work that way (see previous posts on hemoglobin<\/a>, opsins<\/a>, timers<\/a>, this exercise on tubulin<\/a>…).<\/p>\n

Meiosis: a sensible way to divide<\/h3>\n

A machine-based view of the cell carries with it a framework-for-understanding. For example, in looking at meiosis, rather than having students memorize the steps, their characteristics, and how to recognize them in pictures, start from a viewpoint of “what are the cell’s goals here? What\u00a0must<\/em>\u00a0get done?” If two gametes are going to unite to create a new individual of the same species, then the genetic complement of that individual must be equivalent to that of the parents. Lesson: each parent must contribute half \u00a0<\/em>of their holdings such that the offspring will have one full complement.\u00a0Equally important,\u00a0<\/em><\/strong>this cannot be just any half, but must be a half that will precisely complement the half contributed by the other parent. There’s only one way to achieve this effectively: each parent contains two ‘of everything’, and should create particles each holding precisely one ‘of everything.’. One of the best analogies I have heard for this process comes originally from Kim Nasmyth, and has to do with pairing socks<\/a>: briefly, if I have a huge collection of items that I ‘know’ all exist as pairs, but they are jumbled (and for some reason, you and I each demand one of each pair), the best way to proceed is to find sock PAIRS and\u00a0distribute\u00a0one to each of us–a pretty fair summary of homolog pairing in meiosis! Similarly, once we replicate DNA in meiosis, we’re doomed to two divisions to achieve our goal of one-of-everything. Once we set a goal of achieving diversity in gametes, we require randomization events, and indeed find two–the fact that the orientation of each pair of homologs is random (the pole ‘faced’ by maternal-paternal homologs of chromosome 1 is independent of the orientation of the chromosome 2 homologs), and active exchange of genetic information to create ‘patchwork’ chromosomes. This exchange (homologous recombination) must in turn preserve the ‘exactly half’ plan, so the exchange will be between\u00a0matched<\/em> portions of homologs, not random swapping.<\/p>\n

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