Identifying the Stages of Meiosis (Cambridge (CIE) A Level Biology): Revision Note

Identifying the Stages of Meiosis

• Cells undergoing meiosis can be observed and photographed using specialised microscopes

• The different stages of meiosis have distinctive characteristics meaning they can be identified from photomicrographs or diagrams

Meiosis I or Meiosis II

• Homologous chromosomes pair up side by side in meiosis I only

• This means if there are pairs of chromosomes in a diagram or photomicrograph meiosis I must be occurring

• The number of cells forming can help distinguish between meiosis I and II

• If there are two new cells forming it is meiosis I but if there are four new cells forming it is meiosis II

The distinguishing features at each stage of Meiosis I

• Prophase I: Homologous pairs of chromosomes are visible

• Metaphase I: Homologous pairs are lined up side by side along the equator of spindle

• Anaphase I: Whole chromosomes are being pulled to opposite poles with centromeres intact

• Telophase I: There are 2 groups of condensed chromosomes around which nuclei membranes are forming

• Cytokinesis: Cytoplasm is dividing and cell membrane is pinching inwards to form two cells

The distinguishing features at each stage of Meiosis II

• Prophase II: Single whole chromosomes are visible

• Metaphase II: Single whole chromosomes are lined up along the equator of the spindle in single file (at 90 degree angle to the old spindle)

• Anaphase II: Centromeres divide and chromatids are being pulled to opposite poles

• Telophase II: Nuclei are forming around the 4 groups of condensed chromosomes

• Cytokinesis: Cytoplasm is dividing and four haploid cells are forming

Identifying the stages of meiosis table

Stage	Micrograph
Prophase I One group of chromosomes becomes visible as the DNA condenses
Metaphase I Chromosome pairs are located along the middle of the spindle
Anaphase I Whole chromosomes are being pulled away from the middle
Telophase I There are two groups of chromosomes at each pole The nucleus is reforming and the cytoplasm is pinching in
Prophase II Two groups of chromosomes are visible as the DNA condenses
Metaphase II Chromosomes line up along the middle of the spindles in single-file
Anaphase II Chromatids are pulled away from the middle of the spindles
Telophase II There are four groups of chromosomes and the cytoplasm is pinching in

Meiosis I Photomicrographs

Prophase I, Metaphase I , Anaphase I and Telophase I as seen in photomicrographs

Meiosis II Photomicrographs

Prophase II, Metaphase II , Anaphase II and Telophase II as seen in photomicrographs