Heredity

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Heredity
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Heredity Benchmarks

• III.3.MS.1 - Describe how the characteristics of
  living things are passed on from generation to
  generation.
• III.3.MS.2 Describe how heredity and
  environment may influence/determine
  characteristics of an organism.

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Breaking down the Benchmarks

• III.3.MS.1 - Describe how the characteristics of
  living things are passed on from generation to
  generation.
• Chromosome
• Gene
• Hereditary information
• Common traits controlled by a single gene pair.
• Wrinkled or smooth seeds in a pea plant
• Color of horse hair
• Human traits such as tongue rolling

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Breaking down the Benchmarks

• III.3.MS.2 Describe how heredity and
  environment may influence/determine
  characteristics of an organism.
• Inherited Traits
• Acquired Traits

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Heredity Basics

• Heredity is the passing of traits from parent to
  offspring (children).
• The traits are controlled by genes.
• The genes are the chemical code found in helical
  (spiral-shaped) molecules of deoxyribonucleic
  acid (DNA), which are packed away inside the
  cells of all living things.

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Inherited Traits

• Inherited traits are those present in the genetic
  makeup of an organism that have been passed on
  from one generation to the next. These may
  include
• Eye color
• Left- or right-handedness
• Butterfly wing patterns
• Animal fur color

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Acquired Traits

• Acquired traits develop or occur after an
  organism is born.
• They occur in response to environmental factors
  such as stress, overall health, nutritional
  choices, chemical exposure, and changes in land
  use and are not a result of the organisms
  genetic code.
• These include
• Straightened teeth from wearing braces
• The loss of a limb in an accident

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Chromosome

• There are several lengths of DNA in a cells
  nucleus.
• Each one is called a chromosome.

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Chromosome

• There are two copies of each chromosome in every
  cell of an organism.
• One set of chromosomes comes from the mother and
  one comes from the father.

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Gene

• A gene is one area of a chromosome that has the
  instructions to make one protein.
• DNA works by telling a cell how to make the many
  different proteins that your cells need to work.

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Gene

• Each DNA molecule forms a threadlike structure,
  or gene. Genes then in turn form chromosomes.
• There are two copies of each chromosome--one from
  the father and one from the mother.

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Hereditary Information

• We are all familiar with the idea that traits can
  be inherited from parent to child.
• For example, think of dogs a purebred pair of
  Great Danes would never produce puppies with the
  tiny, short-legged characteristics of a dachshund
  -- but what does that really mean?

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Hereditary Information

• Traits are inherited because discrete units
  called genes are passed from parent to child when
  the child is conceived.
• These genes are a unique blueprint for an
  individual organism, providing all the biological
  information needed for its pre-birth development
  and life, as well as for the characteristics that
  make that individual unique.

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Hereditary Information

• Just as in an engine, where the removal of one
  part can disrupt the entire engine's ability to
  run, so the removal of the influence of one gene
  can have a severe effect on the life of an
  organism.

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Gregor Mendel

• In the 1800s Gregor Mendel an Austrian monk
  studied how traits were passed from one
  generation to the next.
• He experimented with plants (green peas).

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How do we know genes exist?

• He kept careful track of the traits displayed by
  the pea plants produced by cross-fertilization,
  discovering that traits of the parent plants were
  inherited by the progeny plants in specific
  patterns.

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Gregor Mendel

• Examination of the trait inheritance patterns of
  the pea plants suggested to Mendel that each
  trait resulted from two units of inheritance.
• Mendel proposed that one unit came from each
  parent plant.
• We now call these units genes.

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Gregor Mendel

• The study of how different forms of a gene affect
  generations of offspring is genetics.
• That is why Mendel is called the father of
  genetics.  

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Gregor Mendel

• Mendel also learned that a particular trait could
  have several varieties that were produced by
  different versions of the "units of inheritance"
  or genes.
• For example, the pea plant flower color could be
  pink or white.
• We use the term allele to designate a version of
  a gene.

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Gregor Mendel

• Mendel's experiments showed that some alleles
  appeared to be dominant over others.
• For example, if a pea plant inherits one pink
  flower color gene and one white flower color
  gene, the resulting flowers will all be pink --
  just as if the plant had two pink flower color
  genes. (Pink is the dominant flower color in
  peas white is the recessive flower color.)

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Gregor Mendel

• If a gene was not dominant then it could be
• recessive
• or even a blend.

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Genotype/Phenotype

• Two other concepts that are useful in
  understanding genetics are
• phenotype
• and
• genotype.

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Genotype/Phenotype

• The phenotype of an organism is its observable
  traits, and these traits are produced by the
  organism's genotype -- or genes -- for that
  trait.
• For example, the pea plant with one pink and one
  white flower gene has the genotype pink/white
  (one pink gene and one white gene) while its
  phenotype is pink (only pink flowers are
  observed).

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Genotype/Phenotype

• Againin simpler terms
• Genotype-What the gene says
• Phenotype-What you see

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Homozygous/Heterozygous

• Homozygous pairs of chromosomes have the same
  gene for a given trait.
• For example, if the gene for brown eyes is B,
  then the homozygous pair would be (BB).
• Heterozygous pairs of chromosomes have different
  versions of a gene for a given trait.
• For example, if the gene for brown eyes is B, and
  the gene for blue eyes is b, then the
  heterozygous pair would be (Bb).

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Homozygous/Heterozygous

• Homozygous gene pair-
• Same
• (BB) (bb)
• Heterozygous gene pair-
• Different
• (Bb)

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Punnet Square
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Inference and Analysis

• Genetics is an elegant and indirect science, but
  it is very powerful. In genetics, inference plays
  a critical role.
• Mendel's experiments led him to infer the
  existence of genes, but he never actually saw
  them.
• Similarly, analysis of mutations, or defects, in
  genes help scientists infer normal gene function.

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Inference and Analysis

• By seeing what happens to organisms when the
  function of a gene is changed, scientists can
  make educated guesses regarding what the normal
  job of the gene is in the cell.

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What kinds of jobs do genes do?

• Genes are responsible for all the functions of
  the cell and are used throughout the life of an
  organism.

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How does Heredity affect You?

• Imagine the phone ringing. Pick it up. Put it to
  your ear. Notice which ear you are using.
• Interlock your fingers. Notice which thumb is
  placed on top. Pull your hands apart and repeat
  the process in reverse order. Notice how
  difficult/awkward it is to have the opposite
  thumb on top.
• Cross and re-cross your arms. Notice which is the
  dominant way you cross your arms.

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What other traits have been passed on to you?

• Handedness (right vs. left)
• Eye color
• Rolling your tongue in a "U" shape
• Free or attached ear lobes
• Widows peak ("V" hairline on forehead)
• Hair on fingers between first and second knuckle
• Cleft chin

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Lets Chart It!

• Wow!! We have inherited a lot of different
  traits.
• Lets collect the data and record it in a chart,
  so that we can better understand that our
  individual traits are a blend of our parents
  genetic information.