Notes: Probability and Heredity

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Notes Probability and Heredity

• Read pgs. 162-167.
• Objective Be able to perform a simple Punnett
  square.

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Genetics

• Heredity the passing of traits/characteristics
  from parents to offspring.
• Genes the part of the DNA that controls a
  certain trait or characteristic. Hair color, eye
  color, freckles, etc.

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Alleles

• The different forms of a gene, represented by
  capital and lower case letters.
• TT, Tt, tt.

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Traits

• Dominant Trait Capital Letter. A trait that
  always shows up in an organism when it is
  present.
• Recessive Trait Lower-case Letter. A trait that
  only shows up in an organism when a dominant
  trait is not present.

Video Testcross
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Dominant and Recessive
TTall tShort Hno hair hhair FFan fnon fan
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Genotype

• Genotype An organisms genetic makeup or allele
  combinations, TT, Tt, tt.
• These are the actual genes in your DNA.

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Phenotype

• Phenotype an organisms physical appearance or
  visible traits, tall or short.
• This is what you look like or what you see.

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Genotype vs. Phenotype
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Homozygous

• Homozygous/Purebred When an organism has two
  identical alleles for a trait, TT or tt.

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Heterozygous

• Heterozygous/Hybrid when and organism has
  different
• alleles for the same trait, Tt.

Donkey
Mule
Video Zygous
Horse
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Codominance

• Codominance is when alleles are neither dominant
  nor recessive, but both are expressed.
• This helps to explain mixed traits such as a
  black chicken and a white chicken mating and
  their offspring are black and white.

Video Codominance
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Punnett Square

• Punnett Square A chart that shows all of the
  possible combinations of alleles from a genetic
  cross.

Video Punnett Squares
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Probability

• Probability is a number that describes how likely
  it is that a certain event will occur.
• When flipping a coin, the probability of it
  landing on heads is 50 and tails is 50.

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Probability

• In a Punnett square, each box represents a 25
  chance of the offspring receiving that genotype.
• Each box represents a 25 chance and there are 4
  boxes. 4X25100.

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Punnett Square
Cross a homozygous tongue roller with a
heterozygous tongue roller. Dominant
Allele Recessive Allele Genotype for homozygous
tongue roller Genotype for heterozygous tongue
roller Genotype outcomes Phenotype outcomes
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Punnett Square
Cross a homozygous tongue roller with a
homozygous non-tongue roller. Dominant
Allele Recessive Allele Genotype for homozygous
tongue roller Genotype for homozygous non-tongue
roller Genotype outcomes Phenotype outcomes
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Punnett Square
Cross a heterozygous tongue roller with a
heterozygous tongue roller. Dominant
Allele Recessive Allele Genotype for
heterozygous tongue roller Genotype for
heterozygous tongue roller Genotype
outcomes Phenotype outcomes