8.1 and 8.2 Notes Chromosomes and Cell Cycle

1. 8.1 and 8.2 NotesChromosomes and Cell Cycle Essential Question How does the cell cycle regulate cell division? 8.1-8.2 notes

2. Standard • B-4.2 Summarize the relationship between DNA, genes, and chromosomes. • B-2.6 Summarize characteristics of the cell cycle: interphase (G1, S, G2) and mitosis (prophase, metaphase, anaphase, telophase); cytokinesis. 8.1-8.2 notes

3. Chromosome Structure • Chromosomes are rod-shaped structures made of DNA and proteins • Each chromosome is a single DNA molecule associated with proteins • The DNA in eukaryotic cells wraps tightly around proteins called histones. • Histones help maintain the shape of chromosomes and aid in the tight packing of DNA • A chromosome consists of two identical halves called sister chromatids. • When the cell divides, each of the two cells receives one chromatid from each chromosome. • Two chromatids are attached at the central point called a centromere. • The centromere holds the two chromatids together until they separate during cell division. 8.1-8.2 notes

4. Section 1 Chromosomes Chapter 8 Chromosome Structure 8.1-8.2 notes

5. DNA andhistones SupercoiledDNA DNA doublehelix Chromatin Chromosomes condense at the start of mitosis. • DNA wraps around proteins (histones) that condense it. 8.1-8.2 notes

6. Cell Division in Prokaryotes • Prokaryotes have cell walls but lack nuclei and membrane-bound organelles. • A prokaryote’s single DNA molecule is not coiled around proteins to form chromosomes. • A prokaryotes DNA is circular chromosome attached to the inner surface of the plasma membrane. • Prokaryotes divided by a process called binaryfission. 8.1-8.2 notes

7. Cell Division in Eukaryotes • In eukaryotic cell division, both the cytoplasm and the nucleus divide. • The are two kinds of cell division: • Mitosis – cell division that results in new cells with genetic material that is identical to the original cell • Meiosis – cell division that results in haploid cells that are genetically different from the parent cell. It occurs in gametes or sex cells. • Mitosis is asexual meaning that it produces offspring from one parent. • All cells except sex cells reproduce by mitosis. 8.1-8.2 notes

8. The Cell Cycle • Cell Cycle • The cell cycle is the repeating set of events in the life of a cell. • The cell cycle consists of cell division and interphase. • Cell division in eukaryotes includes nuclear division, called mitosis, and the division of cytoplasm, called cytokinesis. 8.1-8.2 notes

9. Cell Cycle – Three Parts • Interphase consists of growth (G1), DNA replication, and preparation for cell division (G2). • G1 – period of growth and development • S – DNA is copied (replicated) • G2 – cell prepares to divide • Mitosis – division of the cell nucleus • Prophase – chromosomes condense and nuclear envelope dissolves • Metaphase – chromosomes line up at equator • Anaphase – chromosomes separate and move to the poles • Telophase – chromosomes arrive at the poles • Cytokinesis – division of the cytoplasm 8.1-8.2 notes

10. Interphase • Cells spend most of the cell cycle in interphase. • Following cell division, offspring cells are approximately half the size of the original cell. • During the first stage – G1 phase – offspring cells grow to mature size. • Once cells have reached a mature size, they can enter the S (synthesis) phase. • During the S phase, the DNA is copied (synthesized) • The G2 phase represents the gap between DNA synthesis (S phase) and preceding cell division. • The G2 phase is a time when the cell prepares for cell division. • Cells that exit the cell cycle do not copy their DNA and are said to be in the G0 phase. 8.1-8.2 notes

11. Parent cell centrioles centrosome Interphase • Interphase prepares the cell to divide. spindle fibers nucleus with DNA 8.1-8.2 notes

12. Plant Cells in Interphase 8.1-8.2 notes

13. Prophase • DNA shortens and coils into rod-shaped chromosomes. • Nuclear membrane and nucleolus break down and disappear. • Centrosomes containing centrioles move toward opposite poles of the cell. • Array of spindle fibers called the mitotic spindle begins to form. 8.1-8.2 notes

14. Metaphase • Centrioles move to the poles • Spindle fibers attach to the centromere of chromosome • Chromosomes line up at the equator (middle) of cell 8.1-8.2 notes

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16. Anaphase • During anaphase, sister chromatids separate to opposite sides of the cell. 8.1-8.2 notes

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18. Telophase • During telophase, the new nuclei form • chromosomes begin to uncoil. • Often called reverse prophase because the opposite happens as the cell goes back to normal. 8.1-8.2 notes

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20. Cytokinesis • Cytokines is when the cytoplasm divides • Cytokinesis differs in animal and plant cells. • Plant cells form a new cell plate that splits the cell and animals cells form a cleavage furrow. 8.1-8.2 notes

21. Plant cell Mitosis 8.1-8.2 notes

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25. Control of the Cell Cycle • Checkpoints are times when the cell stops to check and make sure that mitosis is proceeding normally. • G1 checkpoint (cell growth) – • proteins check to see if the cell is healthy and ready to divide. • Healthy cells proceed to the S phase • DNA synthesis (G2) checkpoint • DNA repairs enzymes and checks the results of replication • If ok, then the cell enters mitosis • Mitosis checkpoint • Proteins signal the cell to exit mitosis • Cell then enter G1 phase and the process starts over. 8.1-8.2 notes