Meiosis

Meiosis is the process that produces haploid cells from diploid cells. Meiosis have two key outcomes:

• Reduction Division: It produces daughter cells with fewer chromosomes than the parent cells.
• Recombination: The products of meiosis have different combinations of genes. Genetic recombination give rises to genetically distinct offspring. 

Meiosis is divided into two phases: Meiosis 1 and meiosis 2.

Interphase: Interphase is the same for both meiosis and mitosis. There is the growth, genetic duplication, and formation of structures necessaries for duplication.

Prophase 1: In prophase 1, each pair of homologous chromosomes, in this case non-sister chromatids, align side by side, forming the synapsis. non-sister chromatids exchange pieces of chromosomes, in a process of crossing over.

Metaphase 1: The spindle fibre guide the tetrads to the center of the cell. There they line up in homologous pairs. Each homologous of the pair is positioned in each side of the equator.

Anaphase 1: Homologous pairs are divided from one another, generating lonely chromosomes. 

Telophase 1: DNA is not duplicated in this part.

Meiosis 2: Identical process as mitosis.

Nondisjunction

Sometimes, chromosomes or chromatids do not separate as they should during anaphase 1 or anaphase 2.

• In Anaphase 1, nondisjunction occurs when homologous chromosomes pairs do not separate to opposites poles, instead they all go to they same pole.
• In anaphase 2, nondisjunction occurs when sisterchromatids, fail to be divided, and they go to the same pole together.