Cell Division By: Amber Tharpe

Activation  Humans make 2 trillion new cells per day

Cell Cycle  2 main parts Interphase- Cell is normal Mitosis- Cell is dividing  Cytokinesis- occurs at the end of mitosis

Mitosis  Divides DNA into 2 nuclei  Makes 2 daughter cells with a diploid number  Used for growth and repair  Also used in some asexual reproduction

4 stages (P-M-A-T) 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

Stages of Mitosis (P-M-A-T) Interphase Early Prophase Metaphase Early Anaphase Prophase AnaphaseTelophase

Prophase  DNA condenses  Nuclear envelope dissolves  Spindle fibers start to form

Prophase (in animal cell and onion cell)

Metaphase  Chromosomes align in the middle of the cell (equator)  Spindle fibers attach to the chromosomes to move them

Metaphase

Anaphase  Chromosomes separate to opposite poles  Spindle fibers split chromosomes in half

Anaphase

Telophase  2 nuclear envelopes form around the separated DNA  Spindle fibers dissolve  In animal cells Cell membrane pinches in  In plant cells Cell plate forms which later becomes 2 cell walls

Telophase

Cytokinesis  Cytoplasm and organelles divide  2 cells form

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Animation of Stages of Mitosis

Asexual Reproduction  1 parent  Offspring is identical to parent  Less genetic diversity

Binary Fission  Asexual reproduction for bacteria  DNA is copied in 1 cell  The cell divides into 2 cells with the same DNA

Binary Fission

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Chromosome  Long thread of DNA containing many genes  X- shaped

Somatic cells  Body cells  All cells not involved in reproduction  Diploid cells (2N) Contains 2 copies of each chromosome In humans 46 chromosomes  Made by mitosis

Gametes  Sex cells  Egg (female) or sperm (male)  Haploid cells (1N) Contains 1 copy of each chromosome In humans 23 chromosomes  Made by meiosis  Used in sexual reproduction

 Sex Chromosomes Chromosome pair 23 for gender Either X or Y XX is female XY is male

Sexual Reproduction  Offspring are a mixture of both parents  Occurs by meiosis then fertilization  Meiosis Formation of gametes Makes haploid cells from diploid cells  Fertilization The actual fusion of the 2 gametes First cell is called a zygote

Asexual Reproduction Sexual Reproduction advantages1 parent, requires less energy, fast Increases genetic diversity, increasing the ability to adapt disadvantages Decreases genetic diversity, Less likely to adapt 2 parents, requires more energy, slow

Meiosis  Process of making gametes for sexual reproduction  Events that occur during meiosis allows for greater genetic diversity

Meiosis  Meiosis I Makes 2 unique diploid cells Prophase I – Telophase I  Interphase without duplicating DNA  Meiosis II Makes 4 unique haploid cells Prophase II – Telophase II

Crossing Over  Occurs in Prophase I Homologous chromosomes line up and sections of the chromosomes overlap and become incorporated into the other Allows for genetic diversity

Independent Assortment  Occurs in Metaphase I  Independent Assortment Allows for genetic variation When homologous chromosomes line up in the middle, some chromosomes from the mother and father line up on either side

Telophase II  Produces 4 haploid cells with unique combinations of chromosomes  Females produce 1 ovum (egg) and 3 polar bodies  Males produce 4 sperm cells