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Chapter 3: Genetics – The Science of Heredity

Chapter 3: Genetics – The Science of Heredity. 3.1: Mendel & his Peas. Gregor Mendel Australian Monk born 1822 Studied inheritance Pea plants Each parent contributed something (gene) to offspring Genes had different forms Alleles Ex: plant height could be tall or short.

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Chapter 3: Genetics – The Science of Heredity

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  1. Chapter 3: Genetics – The Science of Heredity

  2. 3.1: Mendel & his Peas • Gregor Mendel • Australian Monk born 1822 • Studied inheritance • Pea plants • Each parent contributed something (gene) to offspring • Genes had different forms • Alleles • Ex: plant height could be tall or short

  3. 3.1: Mendel & his Peas • 2 types of genes • Dominant genes • Stronger trait • Shows w/ one or both dominant genes • Capital letter • Recessive genes • ‘weaker’ trait • Need 2 recessive genes to see trait • lower case letter

  4. 3.1: Mendel & his Peas • Each Parent contributes a gene • 2 copies of same gene (pair) • Example: Mom donates “P” & Dad “p” • 2 letter code represents trait in offspring • PP or Pp  purple • Pp  white • Punnett Square • Shows outcome for all possible parent combinations

  5. 3.2: Mendel & his Peas • Punnett square • Ratio tells probability of results of a cross • Probability is # that describes how likely an event will occur • P = parental generation • Male – top of box • Female – left side of box • F1 generation = kids • F2 generation = grandkids

  6. 3.2: Mendel & his Peas • Genotype • Genetic make up of a trait • Homozygous = both genes same (Pure) • Heterozygous = both genes different (hybrid) • Phenotype • Visible trait • Coded for by genes • Examples…

  7. 10.3: Different Inheritance Patterns • Codominance • Alleles neither dominant nor recessive • In-between (blend) • Write capital letters w/ superscripts • Example: • Red = FR White = Fw • FRFw = pink

  8. 12: Pedigree Charts • Pedigree chart • Genetic history • Used to track a specific trait (phenotype) • Reading a Pedigree chart • Top to bottom = oldest to youngest • Symbols represent individuals • Squares = males • Circles = females

  9. 10: Introduction to Genetics • If DNA = language…. • Nucleic acids = letters • Amino acids = words • Genes = sentence • Chromosome = chapter • All chromosomes (total DNA) = book • Genes occur in pairs • Homologous chromosomes • 1 gene from each parent required for a trait

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