2. Review: History of Genetics
• *1866- Gregor Mendel began the study of
genetics testing the inheritance of traits in the
pea plant.
• * He tested seven different traits:
1. Pea seed color
2. Flower color
3. Seed pod color
4. Seed shape or texture (wrinkled or smooth)
5. Seed pod shape
6. Stem length
7. Flower position
3. Vocabulary Review:
1. A gene or trait that always shows itself is
called _________________.
Dominant Trait
2. A gene or trait that will be hidden when a
dominant trait is present is called ___________.
Recessive Trait
3. A chart that shows possible gene combinations
of offspring is called
Punnett Square
_________________________.
4. Organisms that have two like genes for a
Homozygous
given trait are called _____________.
4. Vocabulary Review:
5. Organisms that have two unlike genes for a
given trait are called ___________.
Heterozygous
6. Another term for an organism that has
two like genes for a certain trait is
_________.
Purebred
7. Another term for an organism that has
two unlike genes for a certain trait is
Hybrid
_______.
5. Complex Patterns of Heredity:
• Some genes to not follow Mendel’s patterns,
some are more complex.
• *Incomplete Dominance- When one gene for a
certain trait is not completely dominant over another
a blending occurs. This is called incomplete
dominance.
7. Complex Patterns of Heredity:
• Sometimes two dominant genes are present
for one trait.
• *Co-dominance:
A pattern of heredity that occurs when two
genes are present for one trait. Neither gene
is dominant or recessive over the other. They
do not blend; they both show up in the
organism.
9. Complex Patterns of Heredity:
• * Multiple Alleles: Many traits are controlled by
more than two possible variations. These traits
are controlled by multiple alleles.
– Example: Human blood groups
10. Complex Patterns of Heredity:
• *Polygenic Trait: Some traits are controlled by
many genes interacting with one another.
These traits are called Polygenic Traits.
– Examples: height, skin color, eye color
