Gregor Mendel

Father of Genetics

How do we acquire our traits?

His Experiments

• Selective cross breeding of pea plants (Pisum sativum)

His findings

• Traits appear without blending– Ex. A purple flower pea plant mixed with a white

flower pea plant would not produce light purple flowers. The results would be: purple or white

Terms:

• Allele: two or more forms of a gene. Example: Pea Color: Green (Y) Yellow (y)

• Dominant: Allele that is expressed or dominant (Y), even in the presence of a recessive allele. Shown by capital letter

• Recessive: Allele that is only expressed when paired with another recessive allele (y). Can be masked, and carried into future generations

• Homozygous: 2 of the same alleles ex. YY or yy• Heterzygous: 2 different alleles ex. Yy• Genotype: Allele description of a trait YY, Yy or

yy• Phenotype: Word description of a trait– YY – Green– Yy – Green– yy - yellow

Terms:

The Principle of Segregation

• Only one gene is passed from the parent to the offspring

Segregation of alleles in the production of sex cells

Principle of Independent Assortment

• Each time a gene is passed, does not depend on the time before.

• Ex. Pea plant could be Yy (a gene for green and a gene for yellow) and Tt (gene for Tall and gene for short)– 1st cross the plant could pass the y– 2nd cross could pass the Y– Passing of the Tall or short gene is INDEPENDENT

of the passing of the color gene

Why do we look similar but different?

Exit Slip

• What do you know now that you didn’t know before class today?

• What did you already know?• What questions do you still have?

More Definitions

• Heredity – traits passed on to the next generation– Ex. Eye color, hair color, shape of hairline, earlobes

attached or unattached, heart disease, diabetes, cancer

• Gene – unit of heredity passed from the parent to the offspring (babies)

• Carrier – carries the recessive gene, but does not show it– Ex. A person can have brown eyes (Bb) but carry the

gene for blue eyes (b)

• Purebred – bred from parents of the same variety (all the same genes!) – Example: TT x TT all tall plants– tt x tt all short plants

• Hybrid – bred from parents with different genotypes (not necessarily different phenotypes)– Tt x Tt could give tall, or short plants