Genetics Notes

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Genetics Notes
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What is heredity?

1. Traits passing from offspring to parents
2. Traits passing from parents to offspring
3. Plants that are cross-pollinated
4. The ratio of dominant to recessive traits

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Heredity is

• C - The passing of traits from parent to
  offspring

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Who was Gregor Mendel?

• Austrian Monk
• Conducted his research in a monastery garden
• Worked with pea plants
• Discovered the principles of heredity

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Self-pollinating Peas

• Self-pollinating when a plant fertilizes itself
• Results in a true-bred plant
• All the offspring of a true-bred plant will have
  the same trait as the parent

Parent
Offspring
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Cross-pollinating Peas

• Pollen from one plant fertilizes the stamen (egg)
  of a different flower on a different plant
• Wind
• Bees other insects

First Generation Plants
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First Generation Plants Self -Pollinated
X
F2 Second Generation
The white flowers reappeared! How did this
happen?
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Alleles different forms of a
gene exist in pairs (one from mom one
from dad)

• Dominant allele the prevailing (stronger) trait
• Capital Letter
• Recessive allele the (weak) hidden trait
• Lower case letter

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• Genotype the combination of alleles you have
  for a specific trait
• Ex RR or Rr or rr
• Phenotype the physical feature you show or see
• Ex Red flower petals, white flower petals

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Example

• Gene Flower Petal Color
• Alleles
• Red (R)
• White (r)
• RR homozygous dominant
• rr homozygous recessive
• Rr heterozygous
• Homo the same Hetero - different

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• Complete Dominance Rr Red
• dominant trait shows
• Co Dominance RW Red White
• Both traits show
• Incomplete Dominance Rr Pink
• Traits are blended (mixed)

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First Generation Plants Self -Pollinated
Rr
X
Rr
Rr
F2 Second Generation
RR
Rr
rr
The white flowers reappeared! HOW? The parents
were heterozygous (Rr).
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Mendels Discoveries

• Each trait has two sets of
• instructions (alleles), one
• from each parent
• Recessive traits reappear
• in the second generation
• when two different
• true-breds are crossed.

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Tommorrow Intro. to Punnett Squares

• A chart used to show all the ways genes from two
  parents can combine and be passed to offspring.