Cell Cycle

1. Cell Cycle

2. **The cell cycle or the cell division cycle is a series of events that take place when a cell is going to divide and reproduce a new cell. This process must take place when: • A fertilized egg develops into a multicellular organism • An organism must replace cells that have been injured or destroyed 3. An organism grows There are 2 main parts to this cycle: • Interphase • Mitotic phase (M phase)

3. SCI.9-12.B-2 - [Standard] - The student will demonstrate an understanding of the structure and function of cells and their organelles.

4. SCI.9-12.B-2.6 - [Indicator] - Summarize the characteristics of the cell cycle: interphase (called G1, S, G2); the phases of mitosis (called prophase, metaphase, anaphase, and telophase); and plant and animal cytokinesis.

6. Chromosomes

7. * • Homologous chromosomes – Chromosomes that have the same type of gene located at the same spot (locus). You inherit one from your mom and one from your dad. They both give you a number one chromosome but dad’s might have a gene for brown eyes and mom’s a gene for green eyes. Alleles – different forms of same gene

9. * Humans have 23 pair of chromosomes. 22 pair of autosomes determine characteristics The 23rd pair determines the sex of the child XX = female XY = male

10. * Genes that are found on the same chromosome are said to be linkedand are inherited together. For example, red hair and freckles are on the same chromosome and are usually inherited together.

11. Structure of a chromosome

12. Chromatids are connected by the centromere and have a LONG AND SHORT ARM. p arm chromatid q arm the entireia a telomere *Chromatids are connected by the centromere and have a LONG AND SHORT ARM. p = short arm q = long arm The ends of the arms are called telomeres. Involved in aging

13. * Centromeres and telomeres are made of short sections of DNA repeated over and over. For example, AAATTT AAATTTAAATTTAAATTT.

15. *INTERPHASE Interphase is when the cell is obtaining nutrients, growing, and making new cellular parts. Inter phase is sometimes called the “resting stage” but it does not rest here. Interphase has 3 parts: G1 – Growth 1 S phase -- when DNA copies itself G2 – Growth 2 the cell is getting ready to divide

16. Plant cell in interphase

17. SCI.9-12.B-2.6 - [Indicator] - Summarize the characteristics of the cell cycle: interphase (called G1, S, G2); the phases of mitosis (called prophase, metaphase, anaphase, and telophase); and plant and animal cytokinesis.

18. .

19. *Prophase • Second stage of cell cycle – the first in the M phase • Everything that appears in this phases will disappear in telophase. Everything that disappeared here will re-appear in telophase

20. *Prophase continued 1. Chromatin condenses (shortens) into chromosomes 2. Centrioles start moving toward poles (ends of cell). 3. Mitotic spindle begins to for1m. 4. The nucleolus disappears. 5. The nuclear membrane disappears. 6. Mitotic spindle is fully formed with chromosomes attached to its fibers. And the chromosomes are all moving toward the center of the cell (called equator).

23. *Metaphase In metaphase, all the chromosomes have their centromeres lined up on the equator.

24. SCI.9-12.B-2.6 - [Indicator] - Summarize the characteristics of the cell cycle: interphase (called G1, S, G2); the phases of mitosis (called prophase, metaphase, anaphase, and telophase); and plant and animal cytokinesis.

25. Plant cell in metaphase

27. *Anaphase In anaphase, the centromere divides and separates the two chromtids. They are now called chromosomes and they move away from the equator toward the poles. (Think A = Away A = anaphase)

28. Plant Cell in Anaphase

30. SCI.9-12.B-2.6 - [Indicator] - Summarize the characteristics of the cell cycle: interphase (called G1, S, G2); the phases of mitosis (called prophase, metaphase, anaphase, and telophase); and plant and animal cytokinesis.

31. *Telophase Telophase is the last stage of mitosis and it is the opposite of prophase. Whatever appeared in prophase, will disappear in telophase and whatever disappeard in prophase will reappear in telophase. 1. Chromosomes go back to chromatin. 2. Mitotic spindle disappears. 3. Nucleolus reforms. 4. Nuclear membrane reforms

32. Plant Cell in telophase

34. *Cytokinesis After the nucleus finishes dividing, the cytoplasm has to divide. It divides evenly down the middle so that the 2 new cells are the same size. In plant cells, the cell wall begins to form first. Then the cell membrane divides.

35. Cytokinesis in plant cells

36. *How long does it take for cells to divide? The more complicated a cell is the longer it takes to divide. Your skin cells take about 10 hours to divide. Some cells in your body do not divide at all. For example, your brain cells are in the G0 phase, meaning they do not divide. Your muscles will not divide again unless they are damaged in some way.

37. SCI.9-12.B-2.6 - [Indicator] - Summarize the characteristics of the cell cycle: interphase (called G1, S, G2); the phases of mitosis (called prophase, metaphase, anaphase, and telophase); and plant and animal cytokinesis.

38. Cells Undergoing Mitosis

39. Interphase Prophase Metaphase Anaphase Telophase