This semester I am teaching two sections of BIOL 1108L, which is second semester biology lab for science majors. Nearly all of my students are sophomore biology majors. About 80% of my students are female, which is why I stressed on the first day of class that women are just as good as men at science, even though they tend to have a lower opinion of themselves.
The course was redesigned this year to focus on inquiry. A large proportion of the students’ grades are determined by the questions they ask and not the answers they give. To help them get an idea about scientific research, I gave them a paper last week to read and discuss.
Because I am an evolutionary biologist and concerned with scientific literacy, I decided to give my students a paper on human evolution. I figured that something on the fusion in human chromosome 2 would be appropriate. Therefore, I settled on the following paper:
Ijdo JW et al. (1991) Origin of Human Chromosome 2: An Ancestral Telomere-Telomere Fusion. PNAS 88: 9051-9055.
We have identified two allelic genomic cosmids from human chromosome 2, c8.1 and c29B, each containing two inverted arrays of the vertebrate telomeric repeat in a head-to-head arrangement, 5’(TTAGGG)n-(CCCTAA)m3’. Sequences flanking this telomeric repeat are characteristic of present-day human pretelomeres. BAL-31 nuclease experiments with yeast artificial chromosome clones of human telomeres and fluorescence in situ hybridization reveal that sequences flanking these inverted repeats hybridize both to band 2q13 and to different, but overlapping, subsets of human chromosome ends. We conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to human chromosome 2.
This fusion is a wonderful example of human evolution. (In fact, Ken Miller used it in his testimony during ID’s Waterloo.) My students seemed to understand this and even mentioned it in their lab notes. However, the paper, which relies on molecular genetics, isn’t too applicable to the ecological experiments that my students will be doing in lab. Nevertheless, I’d still call it a successful class-room exercise because it exposed my students to some human evolution.