Mendelian Genetics

Gregor Mendel a monk that taught natural science to high schoolers - interested in how traits are passed on -Bred snow pea plants to figure it out -Is known as “The father of Genetics” -Genetics- the study of heredity

Why peas? -not too many traits to keep track of -Pea traits-pea color, pea shape, plant height, pod shape, pod color, flower color, flower position

Mendel’s Crosses He crossed purple flowers with white flowers. (True breeding) -all of the resulting flowers were purple (Hybrids, F1 generation) Then he crossed all of the F1 purple flowers together - 75% of the flowers (F2) were purple, 25% of the flowers were white. Where had the white one’s been?? X F1 F2

What does this mean? -these traits are passed on by alleles or genes Mendel’s Laws: Law of Dominance -Dominant Alleles- always expressed (brown eyes) B + B = B B + b = B -Recessive Alleles- expressed only when paired with another recessive allele (blue eyes) b + b = b -homozygous- 2 of the same alleles (b and b) (B and B) -heterozygous- 2 different alleles (B and b)

Mendel’s Laws Con’t -Law of Segregation- homologous chromosomes separate during meiosis. Each gamete gets one allele. Homologous

Law of Independent Assortment- sets of chromosomes line up in metaphase I, independent of other sets of chromosomes Mendel’s Laws Con’t

Blue Eyes b homozygous Brown Eyes BB Bb Homozygous heterozygous B= dominant b = recessive

Allele Expression -genotype- an organisms genetic make up -phenotype- what the organism looks like (the expression of its genes.) Phenotype = SpottedPhenotype = Black Genotype = SS or Ss Genotype = ss S = Spotted s = Black