Target: I will be able to use the principles of dominance to identify the phenotype given a genotype.
Homozygous: When an organism has two of the same alleles for a certain trait.
 For example TT, tt.
Pg. 19

Heterozygous: When an organism has two different alleles for a certain trait.
 For example Tt.
Pg. 23

Genotype: Combinations of gene alleles in an individual.
 TT, Tt, or tt.
Phenotype: Physical expression of genes that determine an individual’s appearance.
 Tall or Short.

• Two organisms can have the same phenotype but different genotypes.
• For example: Both individuals can have Brown eyes, but one can be homozygous (BB) and one can be heterozygous (Bb).
Lets practice!

Trait
Handedness
Right = Dominant
Left = Recessive
Knuckle Hair
Hairy = Dominant
No Hair = Recessive
Cheeks
Dimples = Dominant
No Dimples= Recessive
Genotype
RR
Rr rr
Hh hh
HH dd
DD
Dd
Phenotype
Right Handed
Right Handed
Left Handed
Hairy Knuckles
Not Hairy Knuckles
Hairy Knuckles
No Dimples
Dimples
Dimples

Examples of Inheritable Traits :
• Hairline
• Eye Color
• Tongue Rolling
• Earlobes
• Hitchhiker Thumbs
• Thumb Crossing
• Bent Pinky Finger

Genotype: Combinations of gene alleles in an individual.
 TT, Tt, or tt.
Phenotype: Physical expression of genes that determine an individual’s appearance.
 Tall or Short.
• Two organisms can have the same phenotype but different genotypes. Examples – Tt – tall, TT – tall
 For example: Both individuals can have Brown eyes, but one can be homozygous (BB) and one can be heterozygous (Bb).
Summary:

1. With a partner go through the Studying my Genes Worksheet, helping each other decide which alleles they have and what the genotypes and phenotypes are.
2. Count up their amount of dominant/recessive alleles you have and answer the first question at the bottom of the page.
3. Then using the class data, answer the second question.
4. Finish the worksheet by analyzing what it truly means to be dominant
(question #3)
Pg. 18