Mitosis and Meiosis

What is Mitosis?

• The process of cell division in all diploid cells

• Constantly occurs in cells throughout plants and animals at all times– Muscle cells– Skin cells– Stem cells– Cambium cells

• Results in two diploid daughter cells

Stages of Mitosis

• Interphase• Prophase• Metaphase• Anaphase• Telephase• Cytokinesis

Interphase

• The period of cell growth and function prior to the beginning of true mitosis, in which the cells store energy for cellular division– The cell replicates DNA

and produces chromatid pairs

– This is the longest period in the life of a cell

Prophase

• The first true stage of mitosis• The nuclear membrane dissolves,

centromeres form, and centrioles move toward opposite ends of the cell

Metaphase

• The second and shortest stage of mitosis

• Chromatids align in the center of the cell and spindle fibers attach to centromeres from centrioles

Anaphase

• The third stage of mitosis• Chromatids are separated

and pulled towards opposite ends of the cell by spindle fibers

• Errors in the transmission of genetic information are most likely to occur at this stage

Telephase

• The final and longest stage of mitosis

• Chromosomes reach opposite ends of the cell, and new nuclear membranes form for each new daughter cell

Cytokinesis

• The actual division of daughter cells at the end of mitosis

• A cleavage furrow forms pinching apart cells in animals

• In plant cells, a cell plate forms between daughter cells, dividing cells and forming the new section of the cell wall.

Cytokinesis

What is Meiosis?

• The specialized form of cell division that occurs only in haploid cells – Sperm – Egg– Pollen– Ovum

• Very similar in process to mitosis, except with two cycles, producing 4 haploid daughter cells (23 chromosomes each)

Spermatogenesis

• Production of male sex cells through meiosis

• Produces 4 sperm

Oogenesis

• Production of female sex cells through meiosis

• Usually produces 1 viable egg-other 3 abort

Stages of Meiosis

• Interphase• Meiosis I• Meiosis II• The stages of Meiosis I and Meiosis II are

identical to the stages of Mitosis, but with different cells for a different purpose

Interphase

• Same as mitosis• Period of growth and function

Meiosis I

• Prophase I• Metaphase I• Anaphase I• Telephase I• Cytokinesis

– Reduction process-changes cells from diploid to haploid

Meiosis II

• Prophase II– Prophase II is responsible for aligning

chromosomes for the final division

• Metaphase II• Anaphase II• Telephase II• Cytokinesis