1. Section 3 – Studying Heredity
Simple Genetics
Section 3 – Studying Heredity

2. Pre-Assessment On a whiteboard with your group:
Compare the following pairs and give examples:
Dominant & Recessive
Homozygous & Heterozygous

3. Alleles Alleles Alleles: different versions of a trait
An individual has two copies of a gene – one from each parent

4. Alleles Dominant: expressed form of a trait
Recessive: form not expressed but present
Each gamete contributes one allele to create a two allele offspring

5. Modern Terms Homozygous Heterozygous
When two alleles in a particular gene are displayed as the same
Ex: PP or ww
Heterozygous
When two alleles in a particular gene are displayed differently
Ex: Pp or Ww
PP = homozygous dominant
Ww = homozygous recessive

6. Mid-Assessment On a whiteboard with your group:
Think of ways to remember these opposites:
Homozygous & Heterozygous
Dominant & Recessive
**We will fill out vocabulary

7. Mid-Assessment Think of ways to remember these opposites:
Homozygous & Heterozygous

8. Mid-Assessment Think of ways to remember these opposites:
Dominant & Recessive

9. Modern Terms Cont. Genotype Phenotype
Set of alleles an individual contains for a specific trait
Phenotype
The physical appearance of a character or trait
Pp => purple flower
Genotype Phenotype

10. Post-Assessment In your journal Answer the following questions:
Explain how dominant and recessive traits are represented.
How many alleles does each offspring receive from each parent and how does this selection happen? (Think back to meiosis)
Describe the difference between genotype and phenotype.
Using the letters T and t, write the heterozygous and homozygous form.

11. Pre-Assessment On a whiteboard with your group explain the following:
How do siblings from the same mother and same father look similar but not identical?

12. Recap Dominant - strong or expressed trait
Recessive - “weaker” not expressed
Genotype - the ‘alleles’ that represent physical features
Phenotype - the physical feature

13. Law of Segregation First Law of Heredity
States that – the two alleles of a character segregate (separate) when gametes are formed

14. Law of Independent Assortment
States that – alleles of different genes separate independently of one another during gamete formation

15. Punnett Squares
A diagram that predicts the outcome of a genetic cross by considering all possible combinations
Parents
Father - on top of Punnett Square
Mother - on the side of Punnett Square
Each of the boxes inside are filled with 2-4 letters depending the type of cross
2 – monohybrid
4 - dihybrid

19. Post-Assessment In your journal Answer the following questions:
Complete a Punnett Square cross for a father with heterozygous dominant traits (Pp) and homozygous dominant mother (PP).
Define the percentage of homozygous dominant possibility
Define the percentage of heterozygous dominant possibility
Define the percentage of homozygous recessive possibility
Answer the same questions as above for two heterozygous dominant parents.