The Cell Cycle

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The Cell Cycle
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Genetics Part 1The Cell CycleVocabulary

• Reproduction
• Involves the creation of new individuals
• Cell Theory Revisited
• Cells arise from preexisting cells
• Sexual Reproduction (Sex)
• Involves the combining of genes from two
  different individuals into new arrangements
• Genes are arranged (sorted) into new arrangements.

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Vocabulary II

• Asexual Reproduction
• Sex without the sorting of genes
• Example--when an amoeba divides
• Involves the production of a new organism of
  species from a cell or cells of a single parent.
• Cell Cycle
• An ordered sequence of events in the life of a
  dividing eukaryotic cell.

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Vocabulary III

• Homework Assignment
• Define Budding and list an example/examples of
  where budding occurs.
• Define Fission and list an example/examples of
  where fission occurs.

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Vocabulary III

• Chromosome
• A linear end to end arrangement of genes and
  other DNA
• Chromosome set
• Total number of chromosomes in the chromosome set
• Represented by the letter n
• Chromatid
• One of the two side-by-side replicas produced by
  chromosome division
• Centromere
• Place where chromatids are held together

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Vocabulary IV

• Haploid
• A cell having one chromosome set
• Human Sperm 1 set of 23 chromosomes
• Female Egg 1 set of 23 chromosomes
• In human sex cells n, we represent the chromosome
  set by n
• Diploid
• A cell having 2 chromosome sets
• As an individual, your somatic cells contain 46
  chromosomes (23 23)
• In human somatic cells, we represent the sets by
  2n (2 23 chromosomes)
• Your sex cells still have 1 set of 23 chromosomes

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Mitosis

• Precise duplication of the contents of the parent
  cell nucleus, followed by an orderly separation
  of those contents into two new, identical nuclei.
• Mitosis is asexual reproduction
• Occurs in somatic cells
• Produces 2 daughter cells from each/one parent
  cell

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Cell Cycle Picture 1Three Stages

• Interphase
• G1 phase
• Gap phase 1
• S phase
• DNA synthesis
• DNA is duplicated
• We will cover this after Mitosis and Meiosis
• G2 phase
• Gap Phase 2
• M phase
• Mitotic phase
• PMAT
• Cytokensis

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Cell CycleStep by Step

• Interphase
• Accounts for about 90 of the cell cycle
• Cell grows and and copies its chromosomes in
  preparation for cell division
• G1, S and G2 phase occur

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Cell CycleMitotic Phase (Mitosis)

• Prophase
• Longest of mitotic phase
• Chromosomes condense and become visible
• Chromosomes, once duplicated, are called two
  sister chromatids
• Two chromatids (sister chromatids) are formed by
  one chromosome
• Mitotic spindle assembles

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Prophase
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Prophase
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Metaphase

• Chromosomes align along the middle (equatorial
  plane) of the cell
• Microtubules attach chromosomes to opposite ends
  of the spindle

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Metaphase
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Metaphase
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Cell CycleMitosis

• Anaphase
• Chromosomes are pulled to the poles of the cell
• Sister chromatids are separated
• Centromeres divide
• Telophase
• Nuclei (nucleus) and, nuclear envelope, reforms
  in daughter cells

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Anaphase
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Telophase
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Cell Cycle

• Cytokinesis
• Both daughter cells are separated and two
  distinctive cells are formed.
• Daughter cells are pinched off from each other

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Mitosis Steps
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Mitosis Final Notes

• One cell division resulting in two daughter cells
• Chromosome number, per nucleus, remains the same
• Haploid results in haploid
• Diploid results in diploid
• No crossing over
• More on this in meiosis

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Apoptosis

• Programmed cell death
• Cell shrinks and condenses
• Nuclear envelope disassembles
• Nuclear DNA is broken up into fragments
• Teacher notes
• Gene turned on, suicide proteins are made, chain
  of events occur where key proteins in cell is
  broken down--suicide process regulated by
  surrounding cells in the area to ensure that
  cells survive only when and where they are needed.

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CancerExtra Credit

• Proliferation genes (gas) that promote cell
  division
• Anti-proliferation genes (brakes) that apply the
  brakes of cell division
• Mutation in the proliferation genes, the genes
  that promote cell division, causes the cell to
  divide non-stop--hence a cancer growth or tumor
  is formed