1. Intro To Genetics

2. I. Two things influence who you are: A. Environment B. Heredity

3. II. Gregor Mendel (1822 – 1884) A. Father of genetics
B. Studied inheritance patterns
C. Crosses between pure-breeding pea plants
Pure-breeding – plants produce offspring that are identical to the parent for several generations
Worked with strains that showed two different forms (tall or short plants, green or yellow seeds, etc.)

4. Contrasting traits: 1. tall or short 2. yellow or green
3. roll tongue or not
Diagram on right shows traits Mendel studied (His studies were unique because he only studied 1 trait at a time, he used large numbers of plants to reduce the impact of chance, and used probability to analyze his results. This helped him to recognize distinct patterns of inheritance.)

5. Human Contrasting Traits
Top row, from left to right: Free earlobes and attached, Widow’s peak, Rolled tongue, mid-digit hair
Bottom row: Cleft chin, 2nd toe longer than big toe, hitch-hiker’s thumb, dimples
All shown traits are considered contrasting because they take one of two forms

6. A. Trait: variation of a particular characteristic
III. Basic Vocabulary
A. Trait: variation of a particular characteristic
B. Gene: unit of hereditary information
C. Dominant: gene that masks another gene in a pair (T)
D. Recessive: gene that is hidden by the dominant gene (t)
Must have 2 recessive to show
E. Allele: either member of a pair of genes that determines a single trait
Trait example: tall and short are both traits
Gene: part of DNA that codes for either the tall or short trait
Dominant genes are always capital letters, just need one dominant gene needed to express that trait
Recessive are always lowercase. If T is tall and t is short, then TT and Tt are both tall plants and tt is a short plant
Allele – Tt has one tall allele (T) and one short allele (t)

7. F. Homozygous (purebred): two genes in a pair are identical (TT or tt)
G. Heterozygous (hybrid): a dominant and recessive gene in a pair (Tt)
H. Genotype: genes present (bb)
I. Phenotype: expressed trait (brown)

8. Practice: 1. Which genes are dominant? q R T b N
2. Which gene are recessive?
a m T U
3. Which are heterozygous?
AA Gg Rr PP
Which will show the dominant trait?
Aa BB ff Gg
5. Which will show the recessive trait?
Aa bb ff WW
Dominant = R T N
Recessive – a m
Heterozygous = Gg Rr
Express dominant trait = Aa BB Gg
Express recessive trait = bb ff