Exploring Mendelian Genetics 11-3

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Exploring Mendelian Genetics11-3

• Independent Assortment
• Inheritance Patterns Beyond Simple Dominance

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Quick Review

• Allele each letter (R or r)
• Dominant masks Recessive (Rr or rr)
• Law of Dominance?
• Homozygous RR/rr
• Heterozygous Rr

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Law of Independent Assortment

• States that genes for different traits can
  segregate independently during meiosis
• Gives many more genetic variations
• MEANING If a pea plant is yellow and wrinkled lt
  RrYygt, both sets of alleles will separate
  independently (they work alone!)
• An offspring can receive any combination of rs
  and ys

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Dihybrid Crosses Used For Proof (pg 270/271)
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Incomplete Dominance

• Dominant and Recessive Blend in a heterozygous
  genotype
• Ex Flower Color
• Red (RR) Flower X White (rr) Flower PINK (Rr)
• Can you think of other examples?

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Co dominance

• No recessive, Both traits expressed
• Excoat color
• Heterozygous
• will both be capital
• letters because
• both dominant!

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RRBlack, WWWhite, RWBlack and White Bunny
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Other Ways To Show Genotypes

• Use 2 different letters (all caps)
• Ex BWblack and white bunny
• Use apostrophes to show the other allele
• Ex RR red RR white RRRoan
• (Roan both)
• Found in cows, horses, dogs, etc

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Examples of Roan Animals(co-dominant coat color)
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Multiple Alleles

• Genes with 3 or more alleles
• Ex Blood Typing
• 3 alleles IA, IB, i
• Give 4 possible phenotypes
• A (IAIA, IAi)
• B (IBIB, IBi)
• AB (IAIB)
• O (ii)

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Heres How

• AA A
• Ai A
• BB B
• Bi B
• AB AB
• ii O

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Polygenic Trait

• Several Genes Influence a Trait
• Ex Skin, Weight, Eye Color, Height
• Most genes scattered along the same chromosome
• What causes so many variations?

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Traits Influenced by Environment

• Phenotypes can change based on environment
• Ex Hydrangea Color
• Fur in mammals (color and thickness)
• Height and weight in humans based nutrition