METAPHASE I
PROPHASE I
Centromere
(with kinetochore)
Sister
chromatids
Chiasmata
Metaphase
plate
Spindle
ear
Hope
Tetrad
Microtubule
attached to
kinetochore
Homologous
chromosomes
separate
Tetrads line up
Homologous chromosomes
(red and blue) pair and
exchange segments; 2n = 6
in this example
In crossing over, the DNA
molecules in nonsister chro-
matids break at correspon-
Hing places and then rejoin
the other's DNA.
synapsis, a protein struc-
re called the synaptonemal
mplex forms between
homologues together until
anaphase I.
► The movement of
centrosomes, formation of
spindle microtubules,
breakdown of the nuclear
envelope, and dispersal of
nucleoli occur as in mitosis.