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Mitosis & Meiosis
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Mitosis & Meiosis
Mitosis
- Mitosis enables repair, growth and development
- used in asexual reproduction
- produces cells with identical number of chromosomes and genetic information (46 in humans)
- results in 2 daughter cells, each identical to the parent (clones)
- only one round of cellular division and genetic separation
- daughter cells are diploid (2 sets of chromosomes = 46)
- stages of mitosis
- stage 1: Prophase - contains twice as many chromosomes as before. The chromosomes become shorter and thicker. They each move to the opposite end of the cell
- stage 2: Metaphase - each chromatid pair becomes attached by their centromeres to spindle fibres. Then all chromatid pairs are lined up in the middle of the cell
- stage 3: Anaphase - the centromeres split and the two chromatids of each double chromosome separate. The chromatids of each pair then dragged to the opposite ends of the cell
- Interphase: where the cell spends most of its life living, growing and producing proteins
- stage 4: Telophase: the group of chromatids assemble at the ends of the cell. The spindle fibres disintegrate and a nuclear envelope forms around the chromosomes at each end. A crease (called a cleavage) forms in the middle of the cell and the cell then splits by a process called cytokinesis.
- two new identical cells, called daughter cells, are formed
Meiosis
- for the production of sex cells
- produces gametes for sexual reproduction
- produces daughter cells with half the number of chromosomes of the parent (23 in humans)
- 2 rounds of genetic separation and cellular division
- daughter cells re not genetically identical to the parent cells
- daughter cells are haploid (half of a set of chromosomes)
- occurs in testes and ovaries
- daughter cells have homologous pairs of chromosomes