1. Bell Ringer
A child is born with blue eyes even though BOTH his parents have brown eyes. How is this possible?
Can two blue eyed parents have a brown eyed child? Explain why or why not.

2. Genetics:
The study of heredity

3. Heredity = the passing of traits from parents to offspring

4. Heredity = the passing of traits from parents to offspring
Trait = A feature or characteristic of a person
Physical appearance
Behavior tendencies
Predisposed to medical conditions
A person’s traits are influenced by:
their genetic inheritance
environmental factors
What is a trait?

5. Trait = a feature or characteristic of a person
Physical appearance
Genetics:
Environment:
hair color
eye color
face shape
hair texture
smile shape

6. Trait = a feature or characteristic of a person
Physical appearance
Genetics: genes determine natural hair color
Environment:
hair color
eye color
face shape
hair texture
smile shape

7. Trait = a feature or characteristic of a person
Physical appearance
Genetics: genes determine natural hair color
Environment: sun or hair dyes change hair color
hair color
eye color
face shape
hair texture
smile shape

8. Trait = a feature or characteristic of a person
Behavior tendencies
Genetics:
Environment:

9. Trait = a feature or characteristic of a person
Behavior tendencies
Genetics: genes determine the tendency to use a certain hand
Environment:

10. Trait = a feature or characteristic of a person
Behavior tendencies
Genetics: genes determine the tendency to use a certain hand
Environment:
can learn to use
the opposite
hand

11. Trait = a feature or characteristic of a person
Predisposed to medical conditions
Genetics:
Environment:

12. Trait = a feature or characteristic of a person
Predisposed to medical conditions
Genetics: genes determine a risk of heart disease
Environment:

13. Trait = a feature or characteristic of a person
Predisposed to medical conditions
Genetics: genes determine a risk of heart disease
Environment: eating
healthy foods and
exercising can reduce
risk

14. Trait = a feature or characteristic of a person
Phenotype = a person’s version of a trait
“physical appearance”
hair color: black
eye color: blue
hair texture: straight

15. Practice
List 3 traits Dash has.
List Dash’s phenotype for each trait.

16. Trait = a feature or characteristic of a person
Gene = part of a person’s DNA that influences a trait
Eye color gene
Face shape gene
Hair color gene

17. Gene = part of a person’s DNA that controls a trait
Alleles= different versions of a gene
Eye color gene: brown allele
Eye color gene: blue allele

18. Practice List 3 possible alleles for the hair color gene.

19. Alleles = different versions of a gene
Dominant Allele
Represented by a capital letter
Example: B for brown eyes
Recessive allele
Represented by a lowercase letter
Example: b for blue eyes

20. Alleles = different versions of a gene
All people have 2 alleles for every gene (one from each parent)
Allele of eye color gene from dad
Allele of eye color gene from mom

21. Alleles = different versions of a gene
All people have 2 alleles for every gene (one from each parent)
Genotype = a person’s
combination of alleles
“genetic makeup”
Allele of eye color gene from dad
Allele of eye color gene from mom

22. Genotype = a person’s combination of alleles
A person may inherit 2 of the same alleles = purebred
2 dominant alleles = purebred dominant
Example: B and B
Genotype =
Phenotype =
Mom
Dad E E
Child

23. Genotype = a person’s combination of alleles
A person may inherit 2 of the same alleles = purebred
2 dominant alleles = purebred dominant
Example: B and B
Genotype = BB
Phenotype =
Mom
Dad E E
Child

24. Genotype = a person’s combination of alleles
A person may inherit 2 of the same alleles = purebred
2 dominant alleles = purebred dominant
Example: B and B
Genotype = BB
Phenotype = brown eyes
Mom
Dad E E
Child

25. Genotype = a person’s combination of alleles
A person may inherit 2 of the same alleles = purebred
2 recessive alleles =
Mom
Dad e e
Child

26. Genotype = a person’s combination of alleles
A person may inherit 2 of the same alleles = purebred
2 recessive alleles = purebred recessive
Example: b and b
Genotype =
Phenotype =
Mom
Dad e e
Child

27. Genotype = a person’s combination of alleles
A person may inherit 2 of the same alleles = purebred
2 recessive alleles = purebred recessive
Example: b and b
Genotype = bb
Phenotype =
Mom
Dad e e
Child

28. Genotype = a person’s combination of alleles
A person may inherit 2 of the same alleles = purebred
2 recessive alleles = purebred recessive
Example: b and b
Genotype = bb
Phenotype = blue eyes
Mom
Dad e e
Child

29. Alleles = different versions of a gene
A person may inherit 2 different alleles =
hybrid
Dominant allele masks recessive allele
Example: B and b
Genotype = Phenotype =
Mom
Dad
Mom
Dad e E E e
-or-
Child
Child

30. Alleles = different versions of a gene
A person may inherit 2 different alleles =
hybrid
Dominant allele masks recessive allele
Example: B and b
Genotype = Bb Phenotype =
Mom
Dad
Mom
Dad e E E e
-or-
Child
Child

31. Alleles = different versions of a gene
A person may inherit 2 different alleles =
hybrid
Dominant allele masks recessive allele
Example: B and b
Genotype = Bb Phenotype = brown eyes
Mom
Dad
Mom
Dad e E E e
-or-
Child
Child

32. Practice Brown hair (B) is dominant to blond hair (b). Genotype
Phenotype
purebred dominant
purebred recessive
hybrid

33. Practice Brown hair (B) is dominant to blond hair (b). Genotype
Phenotype
purebred dominant BB
Brown hair
purebred recessive
hybrid

34. Practice Brown hair (B) is dominant to blonde hair (b). Genotype
Phenotype
purebred dominant BB
Brown hair
purebred recessive bb
Blond hair
hybrid

35. Practice Brown hair (B) is dominant to blond hair (b). Genotype
Phenotype
purebred dominant BB
Brown hair
purebred recessive bb
Blond hair
hybrid Bb
Which genotypes are purebred? Which is hybrid?

36. Practice Right-handedness (R) is dominant to left-handedness (r).
What genotype(s) could a right-handed person have?
What genotype(s) could a left-handed person have?
RR or Rr rr

37. Practice
In pea plants, green peas (G) are dominant to yellow peas (g).
What would be the genotype of a:
-purebred green pea?
-hybrid green pea?
-yellow pea? GG Gg gg