Basic Genetic Principles

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Basic Genetic Principles
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Mendel's Cross (Pea Plant Height)
P1 Generation
F1 Generation
F2 Generation
heterozygous
phenotypes
genotypes
homozygous
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F1 (heterozygous) Cross
Tall Tall Tt x Tt
F1 Cross
Punnett Square
F2 Generation
25 TT 25 Tt 25 tT 25 tt
75 tall
25 short
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Punnett Squares
R round r - wrinkled
Round (Rr) x Round (Rr) Heterozygous Cross
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Pedigrees
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Basic Mendelian Genetic Concepts
Rule of Dominance
Law of Segregation

• For any Given Trait, an Individual has 2 Alleles
  (pair of genes)

• Only 1 Allele of the Pair is Expressed

• When Heterozygous, the Expressed Allele is
  Dominant, the Hidden Allele is Recessive

• An Individual Can Only Pass on 1 Allele (one of
  the pair) to the Next Generation

• A Recessive Allele can only be Expressed when
  Homozygous

• Alleles Segregate During Gamete Formation

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Which Color is... Dominant? Recessive?
Which Parent is... Heterozygous? Homozygous?
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Round Yellow Rr Yy
Round Yellow Rr Yy
Dihybrid Cross
X

• 9 round yellow
• 3 wrinkled yellow
• 3 round green
• 1 wrinkled green

75 round 25 wrinkled 75 yellow 25 green
Law of Independent Assortment
The Inheritance of one trait does not effect the
inheritance of another trait
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Dominant Allele
Recessive Allele
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Human Traits