Question

Describe prophase-I of meiosis.

Answer 1

1. Meiosis-1 is preceded by interphase in which DNA is replicated. Meiosis-1 begins with a long prophase.
   
2. During prophase-1 the two homologs are joined together held by a synaptonemal complex of proteins. This forms a tetrad which consists of two homologous chromosomes with two sister chromatids.
   
3. At a later point, the chromosomes appear to repel each other except at the centromere and at points of attachments called chiasmata, which appears in X- shaped.
   
4. These chiasmata reflect the exchange of genetic material between homologous chromosomes, a phenomenon called crossing over.
   
5. This crossing over increases genetic variation by mixing and watching the genes on the homologs.
   
6. In the testis cells of human males, prophase-1 takes about a week.In the egg cells of human females, prophase-1 begins before birth and can continue for 50 years.