Mitosis animation

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Mitosis animation

• www.cellsalive.com

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Meiosis and sexual reproduction

• Chapter 13

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Heredity

• Heredity the transmission of traits from one
  generation to the next
• You have inherited traits from your parentsyou
  also have some variation
• Genetics is the study of these inherited traits.

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Heredity

• What exactly did you inherit?
• Chromosomes, broken into units called genes

Chromosome Long stretch of DNAyou have 23 pairs
Gene one segment of DNAcodes for a specific
protein which causes a specific trait
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How did you inherit these?

• Sexual reproduction

• Egg and sperm have half the number of chromosomes
  (23)haploid (n)
• n 23
• A new human has two copies of each chromosome
  (46)diploid (2n)
• 2n46

Reproductive cells are also called gametes
Egg
Sperm
Fertilization
The diploid cell is called a zygote. Also called
a somatic cell in humans
Zygote
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Human Karyotype

• Homologous chromosomes one from mom/dad, each
  carry the same geneslike eye color
• Are these chromosomes from a diploid or haploid
  cell? How do you know?
• From a gamete or a somatic cell?

Sex chromosomes XX female XY male
Autosomes all the other chromosomes
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Reproduction

• Sexual reproduction two parents give rise to
  offspringnew organism has unique combinations of
  genesmore variation
• Asexual reproduction A single individual is the
  sole parentpasses copies of all its genes to
  offspring.
• New individual is called a clone

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Sexual life cycles are not all like ours
Multicellular Haploid Stages!!!
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Meiosis making gametes

• Very similar to mitosis!
• Making reproductive cells
• Reduces the number of chromosomes from diploid to
  haploid (half the number).
• Two big stages
• Meiosis I and Meiosis II

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Mitosis and Meiosis animations

• http//www.lewport.wnyric.org/JWANAMAKER/animation
  s/mitosis.html
• http//www.lewport.wnyric.org/jwanamaker/animation
  s/meiosis.html

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Meiosis

• Overview
• Chromosomes replicate (only once)
• Homologous chromosomes separate (not sister
  chromatids)
• Cell divides once,
• Cell divides again, more like mitosis
• Result haploid reproductive cells

• Overview pic

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Phases of Meiosis

• Interphase G1, S, G2
• 1. Meiosis I
• Prophase I
• Metaphase I
• Anaphase I
• Telophase and cytokinesis

• 2. Meiosis II
• Prophase II
• Metaphase II
• Anaphase II
• Telophase and Cytokinesis II
• Like mitosis twice (but only replicate chromsomes
  once)

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Phases overview
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Phases overview
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Mini Quiz

• Diagram and name each of the phases of Mitosis.
• What is the function of Meiosis?
• What are three differences between Meiosis and
  Mitosis?

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• http//www.tokyo-med.ac.jp/genet/anm/mimov.gif
• http//www.johnkyrk.com/meiosis.html

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Cross over

• Homologous chromsomes line up next to each other
  forming a tetrad.
• Sections of chromosomes exchange
• Chiasmata criss-crossed regions where cross over
  occurs

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Mitosis vs. MeiosisKey differences

• Synapsis and crossing over
• Homologous chromosomes connecttetrad
• Cross over
• Tetrads line up at metaphase
• Separation of homologous chromosomes

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Meiosis increases genetic variation

• Independent assortment maternal and paternal
  chromosomes can be mixed in gametes (reproductive
  cells)

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Meiosis increases genetic variation

• Cross over produces recombinant chromosomesnew
  combinations of moms and dads
• Random fertilization independent assortment of
  your parents genes when producing a gamete
  results in 8 million possible combos, combination
  of two 64 trillion. You are unique!

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• Why is genetic variation important?

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Mistakes in Meiosis

• Non-disjunction missing or extra chromosomes
• Triploidy
• Down syndrome, 21
• XXY, XYY
• Translocation Missing chunks of chromosome,
  mistake during cross over

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• http//www.people.virginia.edu/rjh9u/ndjanim.html
  

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Mini Quiz Addition

• After modeling meiosis with licorice, diagram the
  phases on your quiz. Use different colors or
  pen/pencil for the chromosomes.
• Be sure to label
• Which chromosome is from mom or dad?
• The names of each phase
• Cross over
• Tetrad