INTRO TO GENETICS
Domestication of wolf
Developing corn & potatoes
Blood contains hereditary
“blood relatives”, “bloodline”
“Renaissance” (17th century)
Parents traits (characteristics) are blended
together in their offspring.
Example: A tall mom and short dad will
produced a child with medium height.
Austrian monk (19th century)
Math, biology, physics
“Father of Genetics"
Peas: the perfect specimen
Produce many offspring
Short life cycle
Easy to control the experiment
Easily identified traits:
Pollen produced in stamen
Egg contained in the pistil
Holds the egg
Pollen grain lands on pistil
and produces a pollen
Sperm travels through tube.
Sperm fertilizes the egg.
Method of Self-fertilization
All possess traits of one
3 of 4 with one parent trait.
1 of 4 with the other parent
Each trait is controlled by a gene.
Two or more alternative forms of a gene (ex. tall &
short). These forms are called “alleles”.
Each trait is the result of a pair of alleles being
Each allele being located on different copies of a chromosome
Example: Tall / tall; tall / short; short / short
Law of Dominance
One allele is dominant over the other
Tall (T) is the dominant allele
Short (t) is the recessive allele
Pure dominant (T / T) and hybrid (T / t) will
produce tall plants.
Only pure recessive (t / t) will produce
Genotype – combination of alleles
Ex.: “T / t”
Phenotype – expression of the allele pair.
Homozygous – allele of pair is the same
Ex.: “t / t”
Heterozygous – alleles of pair are different
Ex.: “T / t”
Law of Segregation
Pairs of alleles separate when “gametes”
(sex cells) are produced.
Example: Hybrids (T / t) will have gametes
with either “T” allele or “t” allele.
Alleles will pair up again during
Ex.: “T” from sperm and “t” from egg will
produce a “T / t” allele pair.
Predicts result between parents.
Law of Independent Assortment
Genes for different
traits are inherited
Ex.: Alleles for
height will not
influence the alleles
for seed color or
Two genes, each that are heterozygous.