1. Simple Punnett Squares
Complete Inheritance
Bio Predict offspring ratios based on a variety of inheritance patterns (including dominance, co-dominance, incomplete dominance, multiple alleles, and sex-linked traits).

2. What is Heredity?
Heredity is the transmission of traits from parents to offspring.
Genetics is the field of biology devoted to understanding how characteristics are transmitted from parents to offspring.

3. The Founder of Genetics
Gregor Johann Mendel, an Austrian monk, founded genetics with his experiments with garden peas.
He discovered heredity where traits from parents are transmitted to the offspring.
Mendel studied 7 characteristics of pea plants and grew plants that were ”pure” for each trait.

4. Mendel’s Discovery
Mendel discovered the following concepts with his studies on pea plants and the heredity of their traits:
P-generation (Parent) – This generation consisted of a cross between 2 plants “pure” for a trait (Tall x Dwarf = TT x tt)
F1-generation (Filial 1) - This generation is the offspring of the p-generation resulting in all tall plants (Tt)
F2-generation (Filial 2) – This generation is the result of a cross between the F1-generation resulting in ¾ tall and ¼ dwarf offspring

5. Mendel’s Conclusion
The F1-generation only ended in tall plants masking the dwarf trait resulting in tall plants being dominant over the recessive dwarf plants.
Law of Segregation states that a pair of factors are separated during the formation of gametes.
Law of Independent Assortment states that factors for different characteristics are distributed to gametes independently.

6. Genetics Vocabulary Alleles – a variation of a gene
Genotype – alleles the organism inherits from the parents represented by letters (AA, Aa, or aa)
Phenotype – physical characteristics/ appearance of the organism as a result from the genotype (tall or dwarf)
Homozygous alleles – both alleles are alike (AA or aa)
Heterozygous alleles – both alleles are different (Aa)

7. Practice! Traits Genotype / Phenotype Homozygous / Heterozygous
Dominant / Recessive
Widows’ Peak Bb aa
Black Fur YY
Freckles

8. The Use of the Law of Segregation
Reginald Punnett discovered the short-hand way to analyzing possible genotypes in offspring utilizing Mendel’s law of segregation.
Punnett Squares (Monohybrid Cross)

9. Punnett Squares
Black fur is dominant to brown fur. Two heterozygous black rabbits mated. What are the possible combinations of the offspring?
Parents: _______ x_______
Genotype Ratio: D:H:R = ____:____:____
Phenotype Ratio: Dom:Rec = ___:___

10. Test Cross
Test Crosses are used to discover the genotype of an unknown individual by crossing the unknown genotype with a genotype that is known (recessive genotype: aa).
If all offspring show the dominant trait, then the unknown genotype is AA.
If the offspring show a mix of the traits, then the unknown genotype is Aa

11. Test Cross Punnett Square
Black fur is dominant to brown fur. A black furred rabbit mated with a brown furred rabbit producing 6 offspring. Four offspring were black furred and 2 offspring were brown furred. What is the genotype of the black furred parent?

12. Honors – Extra Information
The following information will not be on the final exam, but is useful to know for college biology.

13. Dihybrid Crosses
Dihybrid crosses work with 2 traits at a time instead of the typical 1 trait with your regular monohybrid crosses.
What is the dihybrid cross for the following parents?
TtFf x TtFf (Both pea plants are hybrids for being tall and having purple flowers)
What is the phenotypic ratio of this dihybrid cross (DD:DR:RD:RR)?

14. Extra Credit Find the phenotypic ratio of the following crosses:
AABB x aabb
AaBB x AABb
AaBb x aabb
AaBb x AaBb