Mendel and Traits

Genetics is the study of heredity!

Gregor Mendel Grew up in small region of Austria that is now part of the Czech Republic Many remember him as an Austrian monk

Gregor Mendel What did he do? –Bred pea plants to study inheritance Why is his work important? –He discovered the basic principles of heredity –Father of Genetics!

Mendel’s Pea Experiment: Why Peas? 1. Many varieties w/ examinable traits 2. Was able to have strict control over how the pea plants mated 3. Peas plants had many “either/ or” characteristics that could be examined

What is a Trait? What is a trait? - Specific characteristic such as seed color or pod color in a pea plant.

TraitAlleles Seed ShapeRound (R ___)Wrinkled (rr) Seed ColorYellow (Y ___)Green (yy) Seed Coat colorGray (W ___)White (ww) Pod ShapeSmooth (S ___)Wrinkled (ss) Pod ColorGreen (G ___)Yellow (gg) Flower PositionAxial (A ___)Terminal (aa) Plant HeightTall (T ___)Short (tt) Seven Traits Examined by Mendel

7 Traits Examined by Mendel Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Plant Height

Genes vs. Alleles Genes: Location of a specific trait on a chromosome Alleles: alternate forms of a gene with a slight difference in base sequence (A vs. a)

Dominant vs. Recessive Dominant: –In a pair of alleles, when one allele is stronger than the other –This allele is expressed- the one that you can “see” Recessive: –Weaker allele in a pair of alleles –The allele that is hidden Example: The allele for tall pea plants (T) is dominant over short pea plants (t)

Genotype vs. Phenotype Genotype = genetic makeup of an individual (think “gene = genotype”) –Example: the genotype for a pure tall pea plant would be TT Phenotype = the expression of the genotype or the physical characteristics that you can see (think “physical = phenotype”) –Example: If the genotype for height in a pea plant is tt, then you will see a short pea plant.

Homozygous vs. Heterozygous Homozygous –when both alleles in a pair are the same –think “homo = same” –also considered to be “pure” –Example: A pure tall pea plant is homozygous dominant Genotype = TT Heterozygous –when the alleles in a pair are different from each other (think “hetero = different”) –Example: Tall pea plant with genotype = Tt

Genetics Practice: Determining Genotypes and Phenotypes TraitAlleles Seed ShapeRound (R ___)Wrinkled (rr) Seed ColorYellow (Y ___)Green (yy) Seed coat colorGray (W ___)White (ww) Pod ShapeSmooth (S ___)Wrinkled (ss) Pod ColorGreen (G ___)Yellow (gg) Flower PositionAxial (A ___)Terminal (aa) Plant HeightTall (T ___)Short (tt) 1.What is the genotype of a heterozygous axial plant? ______________ 2.What is the genotype of a wrinkled, short pea plant? ______________ 3.What is the genotype of a purebred green pod plant? ______________ 4.What is the phenotype for a ss plant? __________________________ 5.What is the phenotype for a Aa plant? __________________________