Question

Explain the different phases of prophase 1 of meiosis with diagram in detail. (5 MARKS QUESTION).

Answer 1

Most of the events that function to differentiate meiosis from mitosis occur in Prophase I

Homologous chromosomes form bivalents (or tetrads) and crossing over occurs between non-sister chromatids

Prophase I is divided into 5 distinctive sub-stages:

Leptotene – The chromosomes begin to condense and are attached to the nuclear membrane via their telomeres
Zygotene – Synapsis begins with a synaptonemal complex forming between homologous chromosomes
Pachytene – Crossing over of genetic material occurs between non-sister chromatids
Diplotene – Synapsis ends with disappearance of synaptonemal complex; homologous pairs remain attached at chiasmata
Diakinesis – Chromosomes become fully condensed and nuclear membrane disintegrates prior to metaphase I