Cell Division

By: Amber Tharpe

Activation

Humans make 2 trillion new cells per day

Cell Cycle2 main parts

Interphase- Cell is normal

Mitosis- Cell is dividingCytokinesis- occurs at the end of mitosis

MitosisDivides DNA into 2 nucleiMakes 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. Prophase2. Metaphase3. Anaphase4. Telophase

Stages of Mitosis (P-M-A-T)

Interphase Early Prophase

Metaphase

Early Anaphase

Prophase

AnaphaseTelophase

http://micro.magnet.fsu.edu/micro/gallery/mitosis/mitosis.html

Prophase

DNA condensesNuclear envelope dissolves

Spindle fibers start to form

Prophase(in animal cell and onion cell)

MetaphaseChromosomes align in the middle of the cell (equator)

Spindle fibers attach to the chromosomes to move them

Metaphase

AnaphaseChromosomes 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

http://www.classzone.com/cz/books/bio_07/get_chapter_group.htm?cin=2&rg=animated_biology&at=animated_biology&var=animated_biology

Animation of Stages of Mitosis

http://biology.about.com/library/blmitosisanim.htm

Asexual Reproduction

1 parentOffspring is identical to parent

Less genetic diversity

Binary FissionAsexual reproduction for bacteria

DNA is copied in 1 cellThe cell divides into 2 cells with the same DNA

Binary Fission

http://www.classzone.com/cz/books/bio_07/get_chapter_group.htm?cin=2&rg=animated_biology&at=animated_biology&var=animated_biology

Chromosome

Long thread of DNA containing many genes

X- shaped

Somatic cellsBody cellsAll cells not involved in

reproductionDiploid 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 ChromosomesChromosome pair 23 for gender

Either X or YXX is femaleXY is male

Sexual Reproduction

Offspring are a mixture of both parents

Occurs by meiosis then fertilization Meiosis

Formation of gametesMakes haploid cells from diploid

cells Fertilization

The actual fusion of the 2 gametesFirst cell is called a zygote

Asexual Reproduction

Sexual Reproduction

advantages 1 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 cellsProphase I – Telophase I

Interphase without duplicating DNA

Meiosis IIMakes 4 unique haploid cellsProphase II – Telophase II

Crossing OverOccurs in Prophase I

Homologous chromosomes line up and sections of the chromosomes overlap and become incorporated into the other

Allows for genetic diversity

Independent AssortmentOccurs in Metaphase I Independent Assortment

Allows for genetic variationWhen 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