The Cell Cycle continued Chapter 5

·      Chromosomes – Structures within the nucleus of a cell that carry genetic information (DNA). o    There are 46 (23 pairs) in human body cells.   o    There are 23 (unpaired) in sperm and egg cells.

· Chromatin – Strands of DNA wrapped around proteins ·      Chromatin – Strands of DNA wrapped around proteins. (Make up chromosomes).

·      Chromatids – A pair of chromosomes that are identical and become attached. Also called “sister chromatids”. Homologous Chromosomes: Two identical sets.   ·      Centromere – Where sister chromatids attach to each other.

Cell Cycle · Sequence of growth and division of a cell.  1.  Two periods: o    Interphase – period of growth between cell divisions.      70-80% of cell life.      3 parts: ·      1st Growth stage (regular cell function and activity).

Interphase ·      Synthesis stage (DNA is copied). ·      2nd Growth stage (cell parts needed for division are assembled).  

Mitosis Period of cell division.   Nucleus, then cytoplasm divides to form two daughter cells. Both cells are genetically identical to the parent cell.   ·      4 stages of cell division: o    Prophase o    Metaphase o    Anaphase o    Telophase

What happens during each stage of the cell cycle? 1. Interphase: ·      The nucleus can be clearly seen. ·      DNA is copied. ·      Chromosomes cannot yet be seen (still in the form of uncoiled chromatin). ·      Centrioles duplicate themselves.

Prophase Prophase: · Chromatin coils to form visible chromosomes. ·      Nuclear envelope and nucleolus disappear.

Prophase ·      Spindle forms between the pairs of centrioles, which have moved to opposite ends of the cell.

Metaphase Metaphase: · Chromosomes move to the equator. ·      Each chromatid is attached to a spindle fiber by its centromere.

Anaphase     Centromeres split and the sister chromatids are pulled apart to opposite poles of the cell. ·      Each chromatid is now a separate chromosome.

Telophase Final phase of mitosis. · Two daughter cells are formed. ·      Each cell has complete set of chromosomes. ·      Cytoplasm divides (cytokinesis). ·      Nuclear envelope appears, chromosomes uncoil.

Cytokinesis: the splitting of the cytoplasm forming separate cells.