Phases of the Cell Cycle and Mitosis and Meiosis

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Phases of the Cell Cycleand Mitosis and Meiosis
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The Cell Cycle

• Begins with formation of a new cell and ends with
  replication of that cell
• An ordered sequence of events in the life of a
  dividing somatic cell.
• 3 phases
• Interphase
• Mitosis (M) phase
• Cytokinesis (C)
• Mitosis is part of cell cycle.

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Cell Cycle Phase 1

• Interphase
• G1
• Gap, cell grows in size, normal functioning
• S
• Synthesis, DNA replication
• G2
• Cell prepares for division

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The Cell CyclePhase 2

• Mitosis
• Divides nucleus into 2 nuclei
• Each with same chromosome number as the parent
  cell
• For growth and tissue repair
• Asexual reproduction

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4 Phases of Mitosis PROPHASE METAPHASE ANAPHASE T
ELOPHASE
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Mitosis Stages (including interphase) -- IPMAT
Interphase nuclear membrane intact chromosomes
not clearly visible DNA duplicates (92
chromosomes) Prophase chromosomes become
super-coiled and visible Metaphase chromosomes
line up along equator of cell Anaphasecentromere
/ chromosomes divide (back to 46
chromosomes)-separate to opposite
poles Telophase nuclei re-form cell starts to
divide chromosomes uncoil (cytokinesis divides
completely to form two new daughter cells)
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DNA Basics

• Nucleus membrane-bound organelle containing
  genetic information (DNA)
• DNA deoxyribonucleic acid
• Chromosomes-
• structures in the cell that contain genetic
  information in the form of DNA
• Every organism has a distinct (humans 46),
  (goldfish 94)
• Contains 2 chromatids(identical parts)

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Interphase
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Prophase

• Chromosome material coils into chromosomes.

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Metaphase
Chromosomes align in center of cell.
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ANAPHASE

• Each chromatid
• moves towards the opposite pole.

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TELOPHASE - chromosomes gather at the two
poles - nuclear membranes form around 2 new
nuclei
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Example of Mitosis in an animal cell
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Example of Mitosis in a plant cell
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Mitosis Overview
Definition process by which cells divide to
create two identical cells Purpose growth of
the organism and replacement of old cells
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The MITOTIC PHASE 1) MITOSIS -division of
nucleus 2) CYTOKINESIS -division of cytoplasm
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Cytokinesis
Cytoplasm divides completely to form two
daughter cells that have the same number of
chromosomes.
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MEIOSIS

• Cell division that reduces chromosome by half
• Process by which sex cells (sperm / egg) are
  created.
• 2 stages Meiosis 1, Meiosis 2
• sexually reproducing organisms

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Chromosomes

• DNA molecule with its attached proteins
• Chromosome number
• Number of chromosomes in cells
• Differs with species
• Diploid
• 2 of each type of chromosome
• Haploid
• 1 of each type of chromosome

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• Meiosis Phases
• Meiosis comes after G2 of Interphase
• Meiosis I
• Prophase IMetaphase IAnaphase ITelophase I
• Meiosis II (virtually identical to mitosis)
• Prophase IIMetaphase IIAnaphase IITelophase II
• At the end of meiosis four daughter cells are
  produced.
• Each of these resulting daughter cells is haploid
  (egg or sperm have 1/2 DNA of mother cell)

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MEIOSIS I

• A). PROPHASE I each chromosome duplicates
  (called sister chromatids)
• B). METAPHASE I- Chromosomes align at the
  center
• C). ANAPHASE I Chromosomes pairs separate and
  move towards the opposite poles of the cell.
  (sister chromatids stay together)
• D). TELOPHASE I Cytoplasm divides 2 cells are
  formed. Each chromosome is still double stranded.

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Prophase and Metaphase I
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Anaphase and Telophase I
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MEIOSIS II These phases are very similar to the
corresponding mitotic phase.

• PROPHASE II DNA does not replicate
• METAPHASE II chromosomes align in center
• ANAPHASE II Centromeres divide sister
  chromatids migrate separately to each pole
• TELOPHASE II and CYTOKINESIS Cell division
  complete
• Results in four haploid daughter cells.

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Prophase and Metaphase II
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Anaphase and Telophase II
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Summary
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See your Biology Textbook
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• Major differences between mitosis and meiosis
• Mitosis makes two identical daughter cells
• Meiosis makes four cells that are not identical.
  These four cells have half the DNA of the mother
  cell.
• 2) Prophase I of meiosis crossing over occurs,
  making 2 new/unique chromosomes
• 3) Interphase II of meiosis chromosomes do not
  replicate as in interphase I

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Mitosis and Meiosis

• Mitosis Cell duplication
• DNA duplicates, then cell splits into two
• Meiosis Production of sex cells
• DNA duplicates cell splits into two, then again

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