Non-sister chromatids are chromatids from two homologous chromosomes. In prophase I of meiosis two homologous chromosomes pair and this pairing is called synapsis. This allows possible crossing over to occur. Two non-sister chromatids are connected in synapsis by a protein-RNA complex called the synaptonemal complex.
Crossing-over or the physical exchange of chromosome parts might occur and bring to genetic recombination. The sites of crossing-over between nonsister chromatids and are called chiasmata.
A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the sun, Earth and moon are aligned (in "syzygy") exactly, or very closely so, with the Earth in the middle.
