Page 8: Metaphase I and Anaphase I


The metaphase I/anaphase I comparison is made in this pair of images of meiosis in Trillium grandiflorum (n=5) . The top image is of a polar view of metaphase I showing the five bivalents, two of which are labeled A and B respectively for comparison to the bottom image.

The bottom image is of anaphase I and shows the centromeres (large arrows) as well as the chromatid arms (small arrows). Chromosome A1 as well as its homologue (A2) is a metacentric chromosome (i.e., has its centromere located at the midpoint on the chromosome), and shows the four arms of the chromatids joined at the centromeric region. Chromosome B1 as well as its homologue (B2) is a so-called telocentric chromosome (i.e., centromere is located near the telomere), and thus shows only two chromatid arms.