6 3 Mendel and Heredity KEY CONCEPT Mendels

6. 3 Mendel and Heredity KEY CONCEPT Mendel’s research to what we know about genetics today Genetics: study of inheritance patterns and variation. “Father of Genetics”

6. 3 Mendel and Heredity Mendel’s data laid the groundwork for genetics. • Gregor Mendel showed that traits are inherited as discrete units. (without knowing about DNA) • Mendel made three key decisions in his experiments. – used purebred plants – controlled breeding – observed seven “either-or” traits

6. 3 Mendel and Heredity • Mendel used pollen to fertilize selected pea plants – P generation was crossed to produce F 1 generation – interrupted the self-pollination process by removing male flower parts so he could control the traits through pollination to create purebred plants. Mendel controlled the fertilization of his pea plants by removing the male parts, or stamens. He then fertilized the female part, or pistil, with pollen from a different pea plant.

6. 3 Mendel and Heredity • Mendel observed patterns in the first and second generations of his crosses.

6. 3 Mendel and Heredity • Mendel drew three important conclusions (Mendel’s Three Principles) 1. Dominant vs. Recessive • Organisms inherit two copies of each gene, one from each parent. • In many cases, one allele is dominant (or expressed) while the other is recessive (or masked) purple white

6. 3 Mendel and Heredity Mendel’s 3 Principles (continued) 2. Segregation • When meiosis makes sex cells, each cell has only one allele 3. Independent Assortment • Each trait is passed on independent of other traits (creates variety!) Ex: pod color green and seed color yellow

6. 3 Mendel and Heredity Basic Genetics Vocabulary • Chromosome – DNA in coiled form • Gene – Segment of DNA – Contains code for one trait – Occur in pairs (one from each parent) • Allele -Any alternative form of a gene that may occur at a specific gene locus (point)

6. 3 Mendel and Heredity Basic Genetics Vocabulary (continued) • Genome - all of an organism’s genetic material • Genotype – Genetic makeup (the letters) – Example: GG, Gg, or gg • Phenotype – Physical makeup (description) – Example: green or yellow pea • Homozygous alleles: – GG = homozygous dominant – gg = homozygous recessive • Heterozygous alleles: Gg G = green pea g = yellow pea

6. 3 Mendel and Heredity More info on vocabulary • Some alleles are dominant over others • Therefore, 2 genotypes can produce the dominant phenotype • Homozygous dominant (GG) & heterozygous (Gg) both produce green peas

6. 3 Mendel and Heredity Punnett Squares • The Punnett square predicts the probability of traits in offspring IF you know the genotype of the parents.

6. 3 Mendel and Heredity Probability • The chances of an event happening • May be expressed as a ratio, fraction, decimal, or percent Example • Ratio: • Fraction: ___ • Decimal: • Percent: 1: 2 ___

6. 3 Mendel and Heredity A Monohybrid cross examines one trait. • Example: Genotypic Ratio: Phenotypic Ratio: Both parents are heterozygous

6. 3 Mendel and Heredity patterns can be calculated with probability. • Probability is the likelihood that something will happen. number of ways a specific event can occur • Probability = number of total possible outcomes • The more data you have, the closer the actual occurrence will be to the predicted occurrence.

6. 3 Mendel and Heredity 7. 2 Codominance or Incomplete Dominance • In some traits, neither allele is dominant • Example: Japanese four o’clock flowers (incomplete dominance) white, red, pink Notation: White Red Pink WW RR WR (pink) Fw. Fw FRFR Fw. FR(red & white) –for incomplete dominance phenotype is between dominant & recessive (pink flowers) -for codominance, both traits are expressed (flowers will have red areas & white areas)