10.2 and 10.3

The Father of Genetics Gregor Mendel- Austrian Monk and Plant breeder Used pea plants to study how traits were inherited(heredity) Mendel was the first person to trace the characteristics of successive generations of a living thing (pea plants). Because of his work he is regarded as the ‘father of genetics’ ( )

Experiments with Pea Plants Why Peas? Quick reproductive cycle Self-pollinating He studied simple traits, traits that occurred in only one of two possible variations.

Mendel’s Experiment  Gregor Mendel performed cross-pollination in pea plants. Flower color Seed color Pod color Seed texture Pod Texture Height Flower Placement

Mendel’s Experiment Mendel cross pollinated a plant with green seeds and plant with yellow seeds. The F1 generation was all yellow. Mendel allowed the F1 generation to self- fertilize The F2 generation was in a 3:1 ratio of yellow to green seeds

Mendel’s Experiment Mendel concluded that there was two forms of the trait for seed color in pea plants. Yellow and green He called these different forms of the trait alleles From his experiment he determined some forms of a trait were dominant to others. E.g. yellow is dominant to green

Homozygous and Heterozygous Dominant allele = Capital Letter (A) Recessive allele = lower case letter (a) Homozygous= two of the same allele Homozygous dominant (AA) Homozygous recessive (aa) Heterozygous = two different alleles for a trait (Aa)

Genotype vs. Phenotype Genotype Phenotype Allele pair Observable trait (physical features)

Mendel’s Laws Law of Segregation-two alleles for each trait separate during meiosis. Law of Independent assortment- Random distribution of alleles occurs during gamete formation

Monohybrid Crosses Only 1 trait is looked at. Ex: Pod color is the only trait being looked at

Punnett Squares Is a tool Helps us keep track of crosses Allow us to predict possible offspring outcomes

Let’s Practice Red flowers are dominant over white flowers What possible offspring would the following crosses produce? Rr x rr RR x rr Rr x Rr Rr x RR

In guinea pigs dark fur (D) is dominant over light fur (d). What are the genotypes and phenotypes of each of the following crosses? Dd X dd DD X Dd Dd X Dd DD X dd

Punnett Square Practice Brown eyes is dominant to blue eyes. Show a cross between two heterozygous parents. What are the genotypic and phenotypic ratios? Homozygous dominant: Heterozygous: Homozygous Recessive

Brown hair is dominant to red hair. Two parents who are heterozygous want to know the probability of having a child with red hair. What is their probability?

In a family a heterozygous father and a homozygous recessive mother for the trait of freckles. If freckling is a dominant trait, what is the probability that each child is heterozygous?

Dihybrid Crosses Following 2 traits instead of one. When two heterozygous parents are crossed, their offspring are in a 9:3:3:1 phenotypic ratio

Short tails are dominant to long tails and Black fur is dominant to brown fur. SsBb X SsBb

Polyploidy One or more extra sets of chromosomes. Always lethal in humans Earthworms and goldfish can sometime be polyploidy. Wheat (6n), oats (6n), sugar cane (8n)