1. Cell Division and DNA Replication Notes Open the book to pages 132 and 133. You will follow along with the diagram.

2. Cell Division Cell division is the process where one cell becomes two daughter cells. The process is often called the cell cycle because it is repeating. Interphase Mitosis(4 parts) Cytokinesis

3. Why do we need cell division? Cell division is needed for organisms to 1. Grow 2. Replace old cells 3. Repair damaged tissues

4. 1. Interphase: -The cell grows and copies its DNA. Why? Replication is when a cell makes an exact copy of it's DNA. What if it's not exact? See page 132-133

5. 2. Mitosis: 1. Prophase: (Get structures ready) -The double chromatin from interphase condenses to form chromosomes. -Structures called centrioles produce and attach spindle fibers that stretch across the cell. -Finally the nuclear envelope breaks down. What do centrioles and spindle fibers look like?

6. 2. Mitosis: 2. Metaphase: (get set on structures) -Chromosomes attach to the spindle fibers near the center of the cell. Spindle fibers attach to the centromere, which is a structure that holds two identical chromosomes together as a pair. Chromosomes attached by centromeres are called chromatids. Why would the identical chromosomes need to be attached with a centromere?

7. 2. Mitosis: 3. Anaphase (go! to your new home) -The centromeres split with the attached spindle fibers. -The chromatids, now chromosomes, are pulled apart as the cell gets longer.

8. 2. Mitosis: 4. Telophase: (check in and unpack) -New nuclear envelopes develop around the two sets of chromosomes. -The chromosomes unravel becoming chromatin again.

9. 3. Cytokinesis - cyto = cell and kinesis = movement -the cell membrane pinches the middle of the long cell together splitting it into two “daughter cells.” -after cytokinesis the process starts again with interphase.

10. DNA structure and replication -Recall that DNA is wrapped around proteins called histones. -DNA is called chromatin when it is loosely wrapped, forming thin strands. DNA is called chromosome when it is tightly and repeatedly wrapped forming rod-like structures. See video: https://www.youtube.com/watch?v=9kQpYd CnU14 https://www.youtube.com/watch?v=9kQpYd CnU14

11. DNA molecule The DNA molecule looks like a twisted ladder. -The two sides of the ladder are made of alternating phosphate and deoxyribose molecules. (These are the same in all organisms). See pic on p135 -Each step on the ladder is made of two molecules called nitrogen bases. Either Adenine(A) and Thymine(T) or Guanine(G) and Cytosine(C). (The sequence or order of these vary, making unique individuals).

12. DNA replication -Chromatin DNA will “unzip” into two half ladders. Then new nucleotides will pair up with the half ladders to form two complete ladders of DNA. See pic on p136 -Nucleotides are molecules of deoxyribose attached to a phosphate and one of the nitrogen bases.

13. Exact copies of DNA Remember, A always pairs with T and G always pairs with C. If the sequence of nitrogen bases is AGTCACT on the half ladder then TCAGTGA will match it. The other side of the original ladder would have been TCAGTGA so bases that match it would be AGTCACT. This makes them exact copies. See Video: https://www.youtube.com/watch?v=zdDkiR w1PdU https://www.youtube.com/watch?v=zdDkiR w1PdU

14. DNA is unique. Who are you? If you are ATCCCCAGGTCAC TAGGGGTCCAGTG Then ATCCGTTGGTCAC is someone else. TAGGCAACCAGTG

15. Cell Cycle Foldable Fold the sheet so that the circles are next to the letters. Copy the each detail of all phases from the illustrations on pages 132-133. Label the structures in each phase. Add color to make it better Under the heading “what happens...” summarize each stage.