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

Segregation -alleles - variations of the same trait on different chromosomes. Law of Segregation- homologous chromosomes separate during meiosis. Each gamete randomly gets one allele Homologous

Why peas? -not too many traits to keep track of (only 7) -Pea traits-pea color, pea shape, plant height, pod shape, pod color, flower color, flower position

Mendel’s Crosses He crossed true breeding purple flowers (all purple genes) with true breeding white flowers (all white genes). -all of the resulting flowers in the first generation (F1) were purple X F1

Then he crossed all of the F1 purple flowers together - 75% of the second generation (F2) flowers were purple, 25% of them were white. Where had the white one’s been?? Mendel’s Crosses 2 X F1 F2

7 Garden Pea Traits Studied by Mendel

Mendel’s Laws -Dominant Alleles- always expressed (brown eyes) B + B = Brown B + b = Brown

Mendel’s Laws Recessive Alleles- expressed only when paired with another recessive allele (blue eyes) b + b = blue

Homo/ Hetero -homozygous- 2 of the same alleles (b and b) (B and B) -heterozygous- 2 different alleles (B and b)

Allele Expression -genotype- an organisms genetic make up -phenotype- what the organism looks like (the expression of its genes.) Phenotype = ? Genotype =? S =? s =?