Meiosis

Asexual Reproduction

Mitosis

• “budding” aka “binary fission” aka “cloning”
• Only requires ONE parent.
• Offspring are an exact copy of parent.
• Genetically identical
• One cell produces two cells.
• Diploid cells produce more Diploid cells.
• Diploid = cell has two copies of every chromosome.
• Process to make Somatic cells (Body cells) and how simple organisms like bacteria reproduce.

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Sexual Reproduction

Meiosis

• Requires TWO parents.
• Offspring are genetically different from parents.
• One cell produces 4 cells.
• Diploid cells produces Haploid cells.
• Haploid = cell has one copy of every chromosome.
• Necessary to ensure offspring have the correct number of chromosomes.
• Process to make Sex cells which are sperm and egg.
• Aka Germ cells or Gametes

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Asexual or Sexual Reproduction�Which is “better”?

Only One Parent Needed (No Mate)

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Easier (Faster and Less Energy)

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More Offspring / Time

Genetically Identical Offspring =

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NO genetic variation

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NO adaptability

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NO means of evolving (population)

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Genetically Different Offspring =

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genetic variation

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adaptability

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means of evolving (population)

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Two Parents Needed (Mate)

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Difficult (Slower and More Energy)

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Fewer Offspring / Time

Asexual

Sexual

Haploid vs. Diploid

• Humans have a diploid (2N) number of 46.
• What is the haploid (N) number?
• Fruit flies have a haploid (N) number of 4.
• What is the diploid (2N) number?
• Goldfish have a diploid (2N) number of 92.
• What is the haploid (N) number?
• Dogs have a haploid (N) number of 39.
• What is the diploid (2N) number?

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46

8

23

78

Meiosis – 2 cell divisions�Same phases as Mitosis (I-PMAT)

Interphase I:

• Cell grows and DNA replicates�

Homologous Chromosomes: �Pairs of the same chromosome

• one from mom one from dad�

Prophase I:

• Crossing Over
• Creates genetic differences

Metaphase I:

• Homologous pairs line up

Anaphase I:

• Homologous pairs separate

Telophase I:

• Haploid cells produced

Meiosis I

Prophase I

Metaphase I

Anaphase I

Telophase I

Meiosis – 2 cell divisions�Same phases as Mitosis (IPMAT)

• Similar to Mitosis
• DNA does NOT replicate (No new duplication of chromosomes)
• No Interphase II
• Metaphase II:
• Unpaired chromosomes line up
• Anaphase II:
• Sister chromatids separate
• Telophase II/Cytokinesis II:
• 4 cells produced
• Cells are genetically different
• Cells are haploid

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Meiosis II

X

Prophase II

Metaphase II

Anaphase II

Telophase II

Mitosis Vs Meiosis

Mitosis

• Make Somatic (Body) Cells
• Requires only one parent
• Homologous Chromosome do NOT pair up
• NO Crossing Over
• Makes genetically identical cells
• One round of cell division
• 2 cells produced
• Chromosome # stays the same
• Makes Diploid (2N) cells

Meiosis

• Make Gametes (Sex) Cells
• Requires two parents
• Homologous Chromosomes pair up
• Crossing Over Occurs
• Makes genetically different cells
• Two rounds of cell division
• 4 cells produced
• Chromosome # is halved
• Makes Haploid (N) cells

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Both

• Involve division of cells
• Same phases (PMAT)
• Can occur in the same body/organism
• DNA (chromosomes) replicate ONLY once

Mitosis Vs Meiosis

Mitosis

• Make Somatic (Body) Cells
• Requires only one parent
• Homologous Chromosome do NOT pair up
• NO Crossing Over
• Makes genetically identical cells
• One round of cell division
• 2 cells produced
• Chromosome # stays the same
• Makes Diploid (2N) cells

Meiosis

• Make Gametes (Sex) Cells
• Requires two parents
• Homologous Chromosomes pair up
• Crossing Over Occurs
• Makes genetically different cells
• Two rounds of cell division
• 4 cells produced
• Chromosome # is halved
• Makes Haploid (N) cells

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Meiosis with Crossing Over

Meiosis with Crossing Over