Presentation on theme: "Cell Reproduction Mitosis & Meiosis."— Presentation transcript:
Cell Reproduction Mitosis & Meiosis
Mitosis One type of cell division Cell process in which the nucleus divides to form two nuclei identical to each other, and identical to the original nucleus, in a series of steps (prophase, metaphase, anaphase, and telophase)
Mitosis allows for growth and replaces worn out or damaged cells.
Interphase Period of growth & development Hereditary information (DNA) copied (replicated / duplicated) Cells that do not divide (nerves) are always in interphase
Prophase DNA begins to shorten & thicken –Now called chromatids / chromosomes Centromeres form Nuclear membrane breaks apart Spindle fibers form
Metaphase Chromatids / chromosomes line up Centromere attaches to spindle fibers
Anaphase Centromeres divide Spindle fibers shorten Chromatid pairs separate – move to ends of cell Chromatids are now called –Each ½ of the pair is now called a chromosome
Results of Mitosis Division of nucleus –Nuclei are identical to each other Same number & type of chromosomes
Asexual Reproduction A type of reproduction - fission, budding, and regeneration - in which a new organism is produced from one parent and has DNA identical to the parent organism.
Asexual Reproduction Offspring produced from one organism Hereditary information is identical Mitosis is one form of asexual reproduction
Sexual Reproduction Meiosis
Sexual Reproduction A type of reproduction in which two sex cells, usually an egg and a sperm, join to form a zygote, which will develop into a new organism with a unique identity.
Sexual reproduction results in a great variety, or diversity, of offspring.
Meiosis The nucleus divides twice –Meiosis I –Meiosis II
Interphase DNA is duplicated
Prophase I DNA shorten & thicken –Forms chromatids / chromosomes
Metaphase I Copied chromatids / chromosomes line up in middle of cell Centromeres attach to spindle fibers
Anaphase I Chromatid pairs are pulled apart –They DO NOT separate Move to ends of cell
Telophase I Cell divides No further replication of hereditary material
There are now two cells. Both cells have full sets of genetic material (chromosomes)
Prophase II Similar to mitosis –Starts with TWO cells instead of one Spindle fibers appear
Metaphase II Duplicated chromatid / chromosomes line up in middle of cell Spindle fibers attach to centromeres
Anaphase II Centromere divides –Chromatids separate & move to ends of cell Chromatids are now individual chromosomes
Telophase II Spindle fibers disappear Nuclear membranes form at each end of cell Cells divide –Results in 4 cells Each with ½ the original number of chromosomes
In summary: Meiosis Two cells form during meiosis I In meiosis II, both of these cells form two cells The two divisions of the nucleus result in four sex cells (gametes) Each has one-half the number of chromosomes in its nucleus that was in the original nucleus