Chapter 8 Notes

Mitosis  Cells must divide: 1.to keep the surface to volume ratio manageable 2.because if cells get too large, they can not eliminate wastes and bring in proper nutrition.

Diploid – 2 sets of chromosomes (ex. 46 in human body cells) – 2n Haploid – 1 set of chromosomes (ex. 23 in human sex cells) - n

Chromatin and Chromosomes  Chromatin is the thin, threadlike DNA found when the cell is not dividing.  Chromosomes are the thick coiled visible form of DNA found during cell division.  Chromosome

 Study handout. Be able to name and describe each phase and division in cell cycle (front).  Know the order of the phases, and know the labeled structures in mitosis (back).

DNA  In prokaryotic cells, the circular chromosome (DNA) floats in the cytoplasm.  In eukaryotic cells, sets of chromosomes in different lengths (DNA) are found in the nucleus of the cell.

Cell Cycle  During the cell cycle, a cell grows, replicates (copies) all of its DNA, and divides into two daughter cells, which each receives an exact copy of the parent cell’s DNA.  In humans, parent cells have 46 chromosomes, so each daughter cell will have 46 chromosomes.

Cell Cycle  There are 2 main parts of the cell cycle:  1. interphase  2. cell division (mitosis and cytokinesis  Interphase is the part of the cell cycle in which the cell is growing and carrying out its function. This is when the cell is doing its job

Cell Cycle  There are 2 main parts of the cell cycle:  1. interphase  2. cell division (mitosis and cytokinesis  Mitosis is the division of the nucleus  Cytokinesis is the division of the cytoplasm.

Interphase  3 phases of interphase:  1. G1 – Cell growth  2. S – DNA replication  3. G2 – preparation for mitosis; organelles are produced  G1-  S  G2  M  C End part 1

Mitosis - Prophase  PROPHASE:  Chromatin condenses into chromosomes  Nuclear membrane is broken down  Spindle fibers form

Mitosis - Metaphase  METAPHASE:  Chromosomes line up in the MIDDLE of the cell.

Mitosis - Anaphase  ANAPHASE:  The sister chromatids separate and move APART toward the opposite sides of the cell.

Mitosis - Telophase  TELOPHASE:  Chromosomes uncoil into chromatin.  Two new nuclear membranes form.  Opposite of prophase.

Cytokinesis  CYTOKINESIS:  The cell membrane and cytoplasm divide  In plant cells, a cell plate is formed, which turns into a new cell wall.  Animal cells pinch in half.  Result of mitosis: 2 daughter cells that are exactly like the parent cell

A karyotype shows the number of chromosomes and whether it is a boy or girl. Gamete – sex (reproductive) cell – egg or sperm (or pollen) – haploid Somatic cell – body cell - diploid

In meiosis, crossing over takes place when homologous chromosomes exchange segments of DNA.