BY5.1 Meiosis

Meiosis

• involves 2 divisions of the cell
• in meiosis I - 2 daughter cells are produced with half the number of chromosomes of the parental nucleus
• in meiosis II - 2 new haploid nuclei divide again in a division identical to mitosis

result: 4 haploid nuceli formed from the parental nuclei

Interphase:

• occurs when the cell is not dividing
• DNA doubles
• new organelles are formed

Meiosis I:

Prophase I:

• chromosomes split into 2 chromatids
• centrioles move to the poles of the cell
• spindles forms
• chromosomes assocaite into homologous pairs - known as bivalents
• crossing over occurs at chiasmata
• nuclear membrane disintegrates
• nucleolus disappears

Metaphase I:

• pair of homologous chromosomes line up on the equator of the spindle
• maternal and paternal chromosomes are arranged randomly
• random distribution and subsequent independent assortment preoduces new genetic combinations

Anaphase I:

• chromsomes of each bivalent separates and are pulled to the poles
• nuclear envelope…