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  • 1. Basic Genetics Biology
  • 2. Gregor Mendel
    • Austrian Monk
    • Studied pea plants
    • “Father of Genetics”
    • Noticed that plant characteristics occurred in two forms ex. Tall or short stems.
    • Performed crosses by taking pollen from one plant and putting it on the female part of a different plant.
  • 3.  
  • 4. Mendel’s Experiment
    • He crossed a round and wrinkled peas
    • Results: All round offspring
    • What happened to the wrinkled trait?
    • He crossed the round offspring to get the next generation.
    • Results: 75% round, 25% wrinkled
  • 5. Law of Dominance
    • An organism inherits two alleles for a trait (one from mom and one from dad)
    • One allele may hide the expression of the other: It is DOMINANT
    • The allele that is hidden is RECESSIVE
    • R=round (dominant)
    • r=wrinkled (recessive)
  • 6. Law of Segregation
    • During gamete formation (meiosis) the pair of genes separates, so each gamete only has one allele for a trait.
    RR Round pea R R Sperm cells meiosis
  • 7. Vocab Review
    • Phenotype - physical appearance of a trait Ex: widow’s peak, attached earlobes
    • Genotype - pair of alleles inherited
    • Homozygous-two alleles are the same
    • RR or rr
    • Heterozygous-two alleles are different
    • Rr
  • 8. Punnett Square
    • Tool used to PREDICT the outcome of a genetic cross. (hypothesis)
    Possible eggs Possible sperm Possible offspring
  • 9. Steps to follow to solve genetics problems
    • Make a key for ALL the possible genotypes and phenotypes
    • Figure out the parent’s genotypes
    • Figure out the kinds of gametes each parent can make
    • Draw and fill in the Punnett Square
  • 10. Steps to follow to solve genetics problems (continued)
    • 5. List the genotypic ratios of the offspring
    • 6. List the phenotypic ratios of the offspring
    • *these ratios can be fractions or percents
  • 11. Example Problem
    • Mendel crossed a homozygous round and a wrinkled pea plant. Round is dominant.
    • Key
      • RR = round
      • Rr = round
      • rr = wrinkled
  • 12.
    • 2. Parent’s genotypes
    • RR and rr
    • 3. Possible gametes
    R R r r
  • 13. 4. Punnett Square R R r r
  • 14. R R r r Rr Rr Rr Rr
  • 15.
    • 5. Genotypic Ratios: 4/4 Rr
    • 6. Phenotypic Ratios: 4/4 round peas