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Learn about the structure of DNA, the genetic code, genes, cell division, and mitosis. Understand the stages of the cell cycle and the process of cytokinesis. Answer questions about chromosome replication and genetic identity in mitosis.

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Review last week

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  1. Review last week

  2. DNA Structure • Nucleotides have: • A sugar molecule • A phosphate molecule • A nitrogenous base molecule

  3. DNA Structure Each nucleotide has one of four different nitrogenous bases • Adenine (A), Thymine (T), Cytosine (C), Guanine (G) • Which bases pair together? • A with T (vice versa) • C with G (vice versa)

  4. The Genetic Code • DNA has a _______-character code, which form _______________(i.e. GGC) • Each 3 letter word codes for the production of one of 20 different amino acids

  5. Definition • These are a short section of DNA that contains instructions to make a specific protein • GENES

  6. The Cell Cycle

  7. The Cell Cycle • At any moment, there are millions of cells going through cell division • But what about the trillions of cells that aren’t? What are they doing? • They are in some phase of the Cell Cycle

  8. The Cell Cycle

  9. The Cell Cycle • The cell cycle is a sequence of events in the cell from one cell division to another. • The growing and working phase of the cell is called interphase

  10. The Cell Cycle • A cell is in interphase for 90% of the total time of the cell cycle. • During interphase a cell will: • Make copies of each organelle • Make copies of chromosomes (DNA) • Each chromosome and its copies = sister chromatids

  11. Cell Division

  12. Cell Division • What needs to happen in order for cells to divide? • DNA needs to copy itself (chromosomes) • Chromosomes • Thread-like structures containing DNA

  13. Cell division • There are two types of cell division: • Mitosis • Meiosis

  14. Mitosis • One cell splits into two identical daughter cells

  15. What is mitosis for? • Mitosis is used to produce new body cells (eg. for growth and repair). • Simple plants and animals can also use mitosis to reproduce • This is called Asexual reproduction

  16. What happens before mitosis? 1. The chromosomes get thicker

  17. What happens before mitosis? 2. The chromosomes are replicated and can now be seen as x-shapes

  18. What happens in mitosis? 3. The nuclear membrane disappears. The chromosomes line up on the spindle. The chromosomes are pulled to opposite ends of the cell

  19. What happens in mitosis? 4. Each new cell is IDENTICAL to the original and has THE SAME number of chromosomes

  20. Mitosis The stages of mitosis are: • Prophase • Metaphase • Anaphase • Telophase *Each stage has specific details about what is happening to the cell during mitosis

  21. Cytokinesis • Cytokinesis is the second process of cell division • It divides the cytoplasm into two daughter cells

  22. Question 1 • If a cell with 28 chromosomes divides into 2 new cells, how many chromosomes will each new cell have? • 28 chromosomes

  23. Question 2 • True or False . . . The cells produced in mitosis are genetically identical • TRUE

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