GENETICS

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GENETICS

• UNIT 6

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Heredity Genetics

• Heredity the passing of characteristics from
  parent to offspring
• Genetics the branch of Biology that focuses on
  heredity

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Gregor Mendel

• Repeated experiments with pea plants
• Why did he use pea plants?
• Several characteristics in 2 different forms
• Can self or cross fertilize
• Small, grows easily, matures quickly, has lots
  of offspring

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UNDERSTANDING CHECK
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Mendels Experiment

• Monohybrid cross involves one pair of
  contrasting traits
• Example flower color (purple or white)
• Example seed color (green or yellow)

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Mendels Experiment

• Created Parental (P) generation by lots of
  self-fertilization
• Purple, White
• Crossed 2 members of the P generation ? F1
  generation
• All purple
• Self-fertilization of F1 generation ? F2
  generation
• 3 purple 1 white

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Mendels Experiment
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Mendels Hypotheses

• Two copies of gene for each character
• Different versions of gene alleles
• Can have dominant and recessive alleles for a
  character
• Each parent contributes one allele

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Dominant Recessive Alleles

• Use the same letter for one character (Flower
  color)
• Capital letter dominant (Ppurple)
• Lowercase letter recessive (pwhite)

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Other Vocabulary

• Homozygous both alleles are the same
• Heterozygous alleles are different
• Genotype set of alleles
• Phenotype physical appearance

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UNDERSTANDING CHECK
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Mendels Pea Plants

• Character Flower Color
• Dominant Purple (P)
• Recessive White (p)
• P generation genotype PP pp
• P generation phenotype purple white

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UNDERSTANDING CHECK
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Mendels Laws

• Law of Segregation Two alleles separate when
  gametes are formed
• Law of Independent Assortment Inheritance of
  one character does not influence inheritance of
  another

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UNDERSTANDING CHECK
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Punnett Square

• Diagram that predicts outcome of genetic cross
• STEP 1 Write title of cross (parents)
• STEP 2 Set up the square
• STEP 3 Fill in the square
• STEP 4 Write genotype phenotype of offspring

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Patterns of Inheritance

• Crossing heterozygous individuals
• Monohybrid 31
• Dihybrid 9331
• Incomplete dominance

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Incomplete Dominance
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Patterns of Inheritance

• Multiple Alleles genes with 3 or more alleles
• Blood type alleles A, B, O

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Patterns of Inheritance

• Codominance both alleles are expressed
• Roan horse
• Human blood types

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Patterns of Inheritance

• Polygenic traits
• Eye color brown, green, blue
• Surrounding environment