1. Unit 4 Cell Cycle & Mitosis

2. Cell reproduction in multicellular and unicellular organisms
Unicellular: reproduce by binary fission, asexual reproduction
Multicellular: reproduce by cell division; process of growth and repair depend on cell division; also involves the production of sex cells

3. Describe chromosomes Carriers of genetic material found in nucleus
Made up of DNA
Information is copied and passed to future generations
Usually DNA exists as chromatin which are long, winding strands that condense into chromosomes before dividing
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4. Chromosome structure
Chromosomes are made up of two chromatids which are held together with a centromere
Human chromosome number is 46 in body cells (somatic cells); 23 in sex cells (gametes)

11. Describe the cell cycle
Sequence of growth and division in the cell
Consists of 4 phases:
1. G1 phase: growth phase
2. S phase: copying of chromosomes
(DNA replication)
3. G2 phase: growth phase
4. M phase: cell division
Interphase is the growth period where DNA is copied; includes G1, S, and G2
Mitosis: dividing period producing two new cells; happens in M phase
Cytokinesis=division of cytoplasm

12. List and describe the steps of mitosis
Mitosis is the division of the cells (the nucleus, followed by cytokinesis) producing two cells with the same number of chromosomes

13. Prophase Longest phase of mitosis Chromatin coils into chromosomes
The nucleus disappears
Centrioles form and move to opposite poles of cell
Spindle fibers form from centrioles and begins to cross cell

14. Metaphase Chromosomes line up in the middle of the cell
Spindle now forms across the cell

15. Anaphase Spindle fibers begin to shorten This pulls chromosomes apart
Now the chromosome halves are referred to as chromatids

16. Telophase Chromatids reach poles Chromosomes unwind into chromatin
Spindle fibers break down
Nucleolus and nuclei reform
Plasma membrane begins to pinch in

17. Cytokinesis Division of cytoplasm
In animal cells: cell membrane continues to pinch in until two cells are formed
In plant cells: cell plate forms in center of cell and eventually splits cells
At the end of mitosis, two new cells are produced; called “daughter” cells
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