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KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

The student is expected to: 5A describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis, and the importance of the cell cycle to the growth of organisms. KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

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KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

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  1. The student is expected to:5A describe the stages ofthe cell cycle, includingdeoxyribonucleic acid (DNA)replication and mitosis, and theimportance of the cell cycle to thegrowth of organisms

  2. KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

  3. The cell cycle has four main stages. • The cell cycle is a regular pattern of growth, DNA replication, and cell division.

  4. The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis. • Gap 1 (G1): cell growth and normal functions • DNA synthesis (S): copies DNA • Gap 2 (G2): additional growth • Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis) • Mitosis occurs only if the cell is large enough and the DNA undamaged.

  5. Cells divide at different rates. • The rate of cell division varies with the need for those types of cells. • Some cells are unlikely to divide (G0).

  6. Limits to cell growth DNA “overload”: The larger a cell becomes, the more demands the cell places on its DNA. DNA stores the information that controls body functions When a cell is small, DNA can easily control the cell’s functions and meet its needs. When a cell is large, it still only has one copy of DNA, so it is more difficult for the cell to perform its functions.

  7. Exchanging materials: Large cells have more trouble moving substances across the cell membrane. If a cell is too large, it is difficult to get enough oxygen and nutrients in and waste products out Limits to cell growth

  8. Division of the Cell When a cell gets too large, it : 1. makes a copy of its DNA (replication), and then… 2. divides to form two “daughter” cells.

  9. Cell size is limited. • Volume increases faster than surface area.

  10. Surface area to volume ratios 6 1 • 1 X 1 X 1 cube SA:______ volume: _____ • 2 X 2 X 2 cube SA:______ volume: _____ • 10X10X10 cube SA:______ volume: _____ • So when volume doubles, the surface area cannot “keep up” with it 8 24 600 1,000

  11. Surface area must allow for adequate exchange of materials. • Cell growth is coordinated with division. • Cells that must be large have unique shapes.

  12. The student is expected to: 5A describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis, and the importance of the cell cycle to the growth of organisms

  13. KEY CONCEPT Cells divide during mitosis and cytokinesis.

  14. Before a cell gets too big, it will divide to form two “daughter cells” Before a cell divides, it makes a copy of its DNA for each daughter cell.

  15. Cell Division • Cell division in eukaryotes is more complex than in prokaryotes. • There are two stages of eukaryotic cell division • Mitosis: Division of the cell nucleus • Cytokinesis: Division of the cell cytoplasm

  16. 3. Unicellular organisms reproduce asexually by mitosis or something similar to mitosis (prokaryotes cant do mitosis!) a. The daughter cells are identical to the parents cells

  17. Asexual Reproduction • Is one cell reproducing by itself • Two types: • Binary Fission: organism replicates its DNA and divides in half, producing two identical daughter cells • Example: bacteria • Budding: asexual process by which yeasts increase in number

  18. Budding Binary Fission

  19. Chromosomes • Chromosomes are made of condensed chromatin. • Chromatin consists of DNA and the proteins it is wrapped around. • The cells of every organism have a specific number of chromosomes • Ex. humans have 46 chromosomes

  20. DNA andhistones SupercoiledDNA DNA doublehelix Chromatin Chromosomes condense at the start of mitosis. • DNA wraps around proteins (histones) that condense it.

  21. chromatid telomere centromere telomere Condensed, duplicated chromosome • DNA plus proteins is called chromatin. • One half of a duplicated chromosome is a chromatid. • Sister chromatids are held together at the centromere. • Telomeres protect DNA and do not include genes.

  22. At the ends of each chromatid is an area called the telomere. • The telomere is filled with non-coding DNA • Like a protective cap • Gets shorter during each cell division • Shortening is believed to be linked to aging Telomeres

  23. Chromatin v. chromosomes

  24. Chromosomes are only visible during cell division, when they are condensed. The rest of the time the chromatin is spread throughout the nucleus. • Before cell division, each chromosome is replicated (meaning copied) • When a chromosome is replicated, it consists of two identical “sister” chromatids. • When a cell divides the chromatids separate, and one goes to each of the two new cells. • Sister chromatids are attached to each other at the spot called the centromere.

  25. Parent cell centrioles spindle fibers centrosome nucleus with DNA Mitosis and cytokinesis produce two genetically identical daughter cells. • Interphase prepares the cell to divide. • During interphase, the DNA is duplicated.

  26. The Cell Cycle • When a cell is NOT dividing, it is said to be in interphase. • The series of events that a cell goes through as it grows and divides is called the cell cycle.

  27. Events of the cell cycle Interphase, when the cell is NOT dividing, has three phases: G1, S, and G2. • G1 phase: period of activity in which cells do most of their growing. a.Cells increase in size b.Cells synthesize (make) new proteins and organelles • S phase: DNA (chromosomes) is replicated • G2: organelles and molecules required for cell division are produced

  28. M phase is the phase of cell division. This includes: 1. Mitosis, the division of the cell nucleus, which is made up of four segments including prophase, metaphase, anaphase, and telophase. 2. Cytokinesis, or the division of cytoplasm.

  29. G1 phase M phase S phase G2 phase

  30. During prophase, chromosomes condense and spindle fibers form. • Mitosis divides the cell’s nucleus in four phases.

  31. Mitosis There are four phases in mitosis: 1.Prophase a. Longest phase in mitosis (take 50- 60% of total time mitosis requires)b.Chromosomes become visible because they are condensed

  32. c.Centrioles become visible on opposite sides of the nucleus i. The centrioles help organize the spindle, a structure made of microtubules that helps separate the chromosomes ii. Chromosomes attach to the spindle fibers near the centromere iii.Plant cells to not have centrioles but do have mitotic spindles d.Nucleolus disappears e.Nuclear envelope breaks down

  33. During metaphase, chromosomes line up in the middle of the cell. • Mitosis divides the cell’s nucleus in four phases.

  34. 2. Metaphase a.Chromosomes line up in the center of the cell b. Microtubules connect to the centromeres

  35. During anaphase, sister chromatids separate to opposite sides of the cell. • Mitosis divides the cell’s nucleus in four phases.

  36. 3. Anaphase a.Centomeres split and the sister chromatids separate and become individual chromosomes b.Chromosomes move and separate into two groups near the spindle c. Anaphase ends when the chromosomes stop moving

  37. Mitosis divides the cell’s nucleus in four phases. • During telophase, the new nuclei form and chromosomes begin to uncoil.

  38. 4. Telophase a. Chromosomes change form being condensed to dispersed b. A nuclear envelope forms around each cluster of chromosomes c.Spindle breaks apartd. Nucleolus is visible in each daughter nucleus Telophase in the midbodies of two daughter cells

  39. In animal cells, the membrane pinches closed. • In plant cells, a cell plate forms. • Cytokinesis differs in animal and plant cells.

  40. Cytokinesis • Mitosis occurs within the cytoplasm of one cell. • Cell division is complete when the cytoplasm divides. • In plants, a structure called the cell plate forms between the two daughter nuclei. The cell plate develops into a cell membrane and cell wall.

  41. Cytokinesis • In animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into two equal parts. Each part has a nucleus and cytoplasmic organelles. The cleavage of daughter cells is almost complete; this is visualized by microtubule staining

  42. Spindle forming Centrioles Centromere Chromatin Centriole Nuclear envelope Chromosomes (paired chromatids) Interphase Prophase Spindle Cytokinesis Centriole Metaphase Individual chromosomes Telophase Anaphase Nuclear envelope reforming

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