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Similarities and Differences between Mitosis and Meiosis
Mitosis MeiosisWhere does it occur in body?# Cell divisions# DNA replicationsCreates what type of cell?# Chromosomes in End product# Cells producedFunction
Reasons for Mitosis
• Production of 2 daughter cells that are genetically identical
• Provides:– a) a means of asexual reproduction for unicellular
organisms– b) replacement of worn out and damaged cells– c) growth of an organism
Meiosis
• Special type of cell division that produces haploid (n) sex cells (gametes)
• Meiosis is divided into 2 stages: Meiosis I and Meiosis II
• Consists of 1 replication and 2 divisions
Germ Cells• Male
– Sperm producing machines– Germ cells are found in the lining of the
seminiferous tubules (250m in each testicle)– Once they reach maturity, they constantly divide
(Spermatogenesis)
• Female – Germ cells - found in follicles in ovaries and
produced before birth– Cells are suspended in Prophase I and don’t
continue to divide until puberty– Complete their division after being simulated by
hormones during the menstrual cycle (Oogenesis)
Similarities and Differences between Mitosis and Meiosis
Mitosis MeiosisWhere does it occur in body?# Cell divisions# DNA replicationsCreates what type of cell?# Chromosomes in End product# Cells producedFunction
Prophase I
• Nuclear envelope disappears• Replicated chromatin coils into chromatid pairs
• Centrioles move to opposite poles of the cell and start producing protein fibers that form the spindle
Prophase I
• Synapsis – Chromatid pairs attach to form tetrads
• Crossing over – During synapsis, arms of chromatid pairs exchange
segments of DNA at chiasma– Increases genetic diversity
Meiosis I – Anaphase I
• Tetrads separate in an event called disjunction
• Chromatid pairs are pulled to poles of cell• Cleavage furrow begins to form
Meiosis I – Telophase I
• Cleavage furrow formation is complete and cytokinesis occurs
• Nuclear envelope reappears
Meiosis II – Prophase II
• Most cells skip Interphase II and proceed right into Prophase II
• Meiosis II follows the stages of Mitosis
Differences of Meiosis and Mitosis
• Synapsis– Happens in Prophase I– Tetrad formation
• Crossing over– Happens in Prophase I– Arms of chromatids in a
tetrad swap DNA– Increases genetic diversity
• Disjunction– Happens in Anaphase I– Tetrads separate and
chromatid pairs are pulled to opposite sides of the cell
• Non-Disjunction– Happens in Anaphase I– A tetrad does not separate
and sex cells are formed with abnormal chromosome numbers
In which phases will these terms be present?
• Chromatin• Replicated Chromatin• Chromatid Pairs• Tetrads • Chromosomes