mendelian genetics

• Gregor Mendel is an Austrian monk who spent his time in a monastery investigating how individual traits were inherited
• Gregor Mendel used the garden peas (Pisum sativum) in his experiments because it has several traits to be studied, easy to grow, reproduce through self-pollination
• Genetics


  The study of heredity and the factors that affect the transmission of genes to determine inherited characters from one generation to the next
• Heredity


  The transfer of traits genes from parents to offspring
• Seven (7) Different contrasting traits of Garden Peas that Gregor Mendel used in his Study


  • Seed color (yellow or green)
  • Seed shape (round or wrinkled)
  • Flower color (purple or white)
  • Flower position (axial or terminal)
  • Pod color (green or yellow)
  • Pod shape (inflated or constricted)
  • Stem length (tall or dwarf)

  
• Gregor Mendel's Experiment


  1. Produced pure-breeding plants through self-pollination for many generations

  2. Cross-pollinated the peas with contrasting traits
• When green seed peas were self-pollinated, all the offspring produced were all green seed peas
• 7 Different contrasting traits of Garden Peas that Gregor Mendel studied


  • Flower position
  • Pod color
  • Pod shape
  • Seed coat color
  • Seed color
  • Seed shape
  • Stem length

  
• Gregor Mendel's Experiment


  1. Produced pure-breeding plants through self-pollination

  2. Cross-pollinated the pure-breeding plants with contrasting traits

  3. Crossed the hybrid plants (F1 generation)

  4. Produced the second filial generation (F2)
• Parental (P1) generation


  Pure-breeding peas
• First filial (F1) generation


  Offspring from cross-pollination of pure-breeding peas, also called hybrids

  
• Second filial (F2) generation


  Offspring from self-pollination of F1 hybrids
• Monohybrid cross


  A cross using one trait
• In the F2 generation, the ratio of round seeds to wrinkled seeds was 2.96:1 or nearly 3:1

  
• Hereditary "factors"


  Gregor Mendel's term for what are now called genes
• Alleles

  Alternative forms of genes that account for variations in inherited characteristics
• The Law of Dominance


  • One allele is a dominant trait, while the other is a recessive trait
  • Dominant traits hide or mask the appearance of the recessive trait
• Genotype


  The genetic makeup for a particular trait of an organism
• Phenotype


  The observable trait or the visible trait of an organism based on the genotype
• The Law of Segregation

  • Pairs of genes for all traits segregate or separate from each other during meiosis or gamete formation
  • An organism inherits one factor for each trait from each parent
• The Law of Independent Assortment


  • The distribution or assortment of one pair of genes is independent of the distribution of the other pair
  • Traits are inherited independent of each other
• Dihybrid cross


  A cross that involves two pairs of genes or alleles
• How to make a Punnett Square


  1. Make a square and divide into 4 boxes for monohybrid cross and 16 boxes for dihybrid cross

  2. Write the possible genes from the female on the left side

  3. Write the possible genes from the male across the top

  4. Cross the male and female gametes in each box

  5. Place the phenotype below each genotype

  
• The genotypic ratio from the dihybrid cross example is 1:2:1:2:4:2:1:2:1
• The phenotypic ratio from the dihybrid cross example is 9:3:3:1
• Punnett square


  1. Show the given cross

  2. Fill up the blank boxes
• Genotype


  The genetic composition for a trait of an organism
• Phenotype


  The observable trait or visible feature of the organism
• Possible offspring genotypes


  • LL (homozygous long stem)
  • Ll (heterozygous long stem)
  • ll (homozygous short stem)

  
• Possible offspring phenotypes


  • Long stem
  • Short stem
• Oval face (O) in man is dominant over round face (o)
• Punnett square


  Show the cross between homozygous oval-faced man and homozygous round-faced woman
• Possible offspring genotypes


  • OO (homozygous oval face)
  • Oo (heterozygous oval face)
• Phenotypic ratio


  The ratio of the different observable traits in the offspring
• 0% of their children will be round faced
• Punnett square


  Show the cross between homozygous stickup-eared dog and homozygous dropped-eared dog
• Possible offspring genotypes


  • Ee (heterozygous stickup ears)
• Possible offspring phenotypes


  • Stickup ears