Mitosis and Meiosis

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Mitosis and Meiosis

• By Richard Shirk, Jr.

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What Are Mitosis And Meiosis?

• Both are types of reproduction used during the
  cell cycle
• Each type of cell division are specialized for
  different types of cells
• Both undergo the cell cycle in very similar, yet
  very different ways

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Important Definitions

• DNA a molecule composed of deoxyribose
  nucleotides and contains the genetic information
  of living cells
• Chromosome a single DNA double helix together
  with proteins that help to organize the DNA
• Chromatid one of the two identical strands of
  DNA and protein that forms a replicated
  chromosome
• Gene a unit of heredity specifies the amino
  acid sequence of proteins and hence particular
  traits
• Allele one of several alternative forms of a
  particular gene
• Locus the physical location of a gene on a
  chromosome

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Important Definitions (cont.)

• Diploid referring to a cell with pairs of
  homologous chromosomes
• Haploid referring to a cell that has only one
  member of each pair of homologous chromosomes
• Homologous Pair two homologues that are similar
  in appearance and genetic information that pair
  during meiosis
• Heterozygous carrying two different alleles of
  a given gene
• Homozygous carrying two copies of the same
  allele of a given gene

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Mitosis

• Mitosis is the division of chromosomes in a cell
• Usually followed by cytokinesis or cell division
• Daughter cells produced after mitosis have same
  number of chromosomes as original cell
• Purpose of mitosis is replication of somatic
  cells and asexual reproduction
• Somatic cells include all cells in the body
  except the egg or sperm

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Meiosis

• Meiosis is the division and reduction of the
  chromosomes of a cell
• Daughter cells produced have half the chromosomes
  as the original cell
• Purpose of meiosis is the production of gametes
  (sex cells)

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Stages Of The Cell Cycle

• Interphase
• Synthesis
• Prophase
• Metaphase
• Anaphase
• Telophase

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Interphase And Synthesis Stages Of Mitosis And
Meosis

• During Interphase the cell carries out normal
  activities such as metabolism and protein
  synthesis
• During synthesis the DNA in each chromosome is
  replicated

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Prophase And Metaphase Stages of Mitosis

• The prophase stage
• chromosomes condense and would be visible under
  a light microscope
• the nuclear membrane degrades
• In the metaphase stage the chromosomes line up
  along the equator

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Anaphase And Telophase Stages of Mitosis And
Cytokinesis

• In the anaphase stage the sister chromatids
  separate and move to opposite ends of the cell
• In the telophase stage one set of each chromosome
  reaches each pole
• Cytokinesis begins and the cell divides in two
  creating two diploid cells

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Meosis I

• Prophase I
• chromosomes visible
• hHomologous pairs of chromosomes come together to
  from tetrads
• crossing over occurs when a chromatid of one
  chromosome in a pair exchanges a segment of
  itself with the chromatid of the other chromosome
  in the pair

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Meosis I (cont.)

• Metaphase I
• homologous pairs line up along the equator of the
  cell
• Anaphase I
• Homologous pairs of chromosomes separate and move
  to opposite poles of cell
• Telophase I
• Chromosomes complete their migration to poles of
  the cell and cytokinesis occurs

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Meosis II

• No new DNA replication takes place
• Prophase II
• Spindle fibers re-form and chromosome begin to
  move to middle of cell

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Meosis II (cont.)

• Metaphase II
• chromosomes line up along equator
• Anaphase II
• sister chromatids of each chromosome separate and
  move to poles of cells
• Telophase II
• the chromatids complete migration
• nuclei reform and cytokinesis occurs
• Meosis produces four haploid cells

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Crossing Over Of Meosis

• Increases the number of allelic combinations
• Increase in different possible physical
  expressions and characteristics
• Allows species to try varies combinations and
  find the best combination that suits their
  environment

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Works Cited

• http//genetics.nbii.gov/Basic1.html
• http//www.biologycorner.com/bio4/notes/meiosis.ph
  p
• http//www2.mcdaniel.edu/Biology/PGclass/mitosis/p
  g3bd.htm