Study Notes Mitosis

STUDY NOTES MITOSIS

Vocabulary

Cell cycle- The pattern of growth, DNA replication and cell division in a eukaryotic cell.

Mitosis- Cell Division

Centromere- The center of sister chromatids where they are attached.

Centrioles- small cylinder shaped organelles that aid in mitosis.

Sister chromatids- Duplicate chromosomes

Stem cells- Cells that can divide for long periods without differentiating.

Cloning- the process of making exact genetic copies.

Cell Cyle (3 stages)-Interphase, Mitosis, Cytokinesis

Interphase (3 stages)

1. G1- Gap 1- cell grows in size, synthesizes proteins

2. S-synthesis phase-chromosomes replicate and divide to form sister chromatids

3. G2-Gap 2-cell grows, organelles double, synthesizes proteins

Mitosis (4 stages)

1. Prophase-chromosomes condense, nuclear membrane disappears, centrioles separate, spindle fibers form, longest phase of mitosis

2. Metaphase- chromosomes line up at the equator, spindle fibers attach to the centromeres on the chromosomes

3. Anaphase-sister chromatids separate at the centromere, chromosomes move to opposite poles of the cell

4. Telophase—last stage, chromosomes uncoil back into chromatin, nuclear membrane reforms, spindle fibers dissolve, cytokinesis begins

Prophase Metaphase Anaphase Telophase

Cytokinesis

Animal cells- cell membrane pinches in forming the cleavage furrow until two cells are formed

Plant cell- a cell plate is formed to divide the cell into two cells

Cell Division/Cell Differentiation

Cell Division-only leads to increasing numbers of identical cells

Cell differentiation- becoming specialized in structure and function

Stem Cells-Embryonic, only found in embryos. Adult-only found in adults(bone marrow)

Cloning- Pros organ transplants and saving endangered species. Cons- may result in a new organism.

STUDY NOTES MEIOSIS

Vocabulary Meiosis- Cell division that produces sex cells. Results in 4 gamete cells with half the number of chromosomes. Occurs in sex organs(testes/ovaries). Sister Chromatids Homologous Chromosomes-two chromosomes one from mom, one from father Diploid-Containing 2 sets of chromosomes Haploid-Containing 1 set of chromosomes Tetrad-Group of 4 chromosomes (homologous pairs) Gametes-a sex cell Oogenesis- the process of cell division that results in an egg Spermatogenisis-the process of cell division that results in a sperm Crossing over- Crossing over: segments of nonsister chromatids break and reattach to the other chromatid

Why is Meiosis necessary?- Shuffles traits from parents to create new combinations in offspring Provides genetic variation in species MEIOSIS I INTERPHASE DNA replication occurs Cell Growth PROPHASE I Chromosomes condense, nuclear membrane disappears, spindle fibers form, centrioles separate Homologs pair up and form a tetrad Crossing over occurs METAPHASE I Shortest phase Paired homologues align in middle of the cell Independent assortment occurs: Each pair of homologues lines up independent of other pairs ANAPHASE I Homologous chromosomes separate and move towards the poles. Sister chromatids remain attached at their centromeres (still duplicated but haploid). TELOPHASE I Nuclear membrane reforms, Cytokinesis begins, spindle fibers breakdown. Each pole now has haploid set of chromosomes (however – still duplicated). Cytokinesis occurs and two haploid daughter cells are formed.

Prophase I Metaphase I Anaphase I Telopahse I

MEIOSIS II No interphase II ( no more DNA replication) Remember: Meiosis II is similar to mitosis PROPHASE II spindle forms, NM breaks up, centrioles separate. METAPHASE II sister chromatids line up at the midline and spindle fibers attach to centromeres ANAPHASE II sister chromatids separate and move to opposite poles. TELOPHASE II Same events as telophase in mitosis. Nuclear membrane reforms, spindle dissolves, chromosomes uncoil, Cytokinesis occurs (2nd time) Four haploid daughter cells produced with only 1 set of chromosomes that are not duplicated. Gametes ~ sperm or egg

Prophase II Metaphase II Anaphase II Telophase II

GAMETE FORMATION IN ANIMALS Female: oogenesis Uneven amounts of cytoplasm are given to the cells Male: spermatogenesis during the 2 times cytokinesis occurs in meiosis. Most of the cytoplasm goes into 1 of the cells all 4 products of meiosis develop into sperm cells resulting in a large egg cell and 3 small “polar bodies” Polar bodies break down and get rid of extra chromosomes.

SPERMATOGENESIS OOGENESIS n=23 23 human human germ cell n=23 Sperm in ovary Polar n=23 23 Bodies germ cell in n=23 Still doubled Still doubled 2n = 46 Haploid (n) testes chromosomes 2n = 46 23 n=23 n=23 diploid (2n) n=23 Still doubled Still doubled n=23 diploid (2n) Ovum chromosomes meiosis I meiosis II n=23 meiosis I meiosis II

Mitosis Meiosis

2 daughter cells 4 daughter cells

Each with same # & kind of Each with ½ chromosome number as chromosomes as parent cell parent cell (1 of each homologous pair) One division process Two divisions

One cytokinesis Two cytokinesis events

Body (somatic cells) Germ tissue forms gametes (sperm & egg)

Identical cells produced Different cells produced

No paring of homologues or Homologues pair & crossing over crossing over occurs in prophase 1