1. Dominant, Recessive, Heterozygous, Homozygous
First Five!
Catalyst:
Ronnie has a deep voice.
Is this genotype or phenotype? Explain how you know.
Brandy has one allele for being tall, and one allele for being short.
If you do not know the answer, use a textbook to figure it out.

2. Agenda Genotype and phenotype review Principal of Dominance
Abbreviating Genotypes and Phenotypes
Practice
Exit Question

3. Objectives By the end of today, all SWBAT…
Differentiate between homozygous and heterozygous genotypes
Determine the phenotype of an organism, based on its genotype

4. From the sub work… Genes: Pieces of DNA you inherit from parents.
Chromosome  Genes  DNA
Alleles: Different versions of genes.
Genotype
Combination of alleles inherited from parents
(1 from mom, 1 from dad)
In your GENES
Phenotype
PHYSICAL showing of your genes
Traits

5. “Principle of Dominance”
Key Point #1: Dominant alleles mask recessive alleles.
Dominant alleles make it like the recessive allele isn’t there.
2 dominant alleles = dominant phenotype
2 recessive alleles = recessive phenotype
1 of each = dominant phenotype

6. Principle of Dominance example
GENE: Hair color
Dominant: Brown Recessive: Blonde
Alex has two dominant alleles. His hair is brown.
Katlyn has two recessive alleles. Her hair color is blonde.
Amber has one dominant allele and one recessive allele. Her hair is BROWN!!!

7. Check for Understanding
Long fingers are dominant, short fingers are recessive. What is the phenotype (type of fingers) of each student?
Arcynee has two dominant alleles.
Eric has one dominant allele and one recessive allele.
Austin has two recessive alleles.
Tyikia has one dominant allele and one recessive allele.

8. Check for Understanding
Long fingers are dominant, short fingers are recessive. What allele combination (genotype) each student have?
Darien has long fingers.
Helen has short fingers.

9. But Ms. S, I’m Lazy!
Key Point #2: There are three rules for abbreviating genotype
Dominant allele = CAPITAL letter
Recessive allele = lowercase letter
BOTH alleles use the same letter
Example: Long tails in dogs are dominant, short tails are recessive.
Long = L
Short = l

10. Dominant and Recessive Genotypes
For every gene you have two alleles, and each of those could be dominant or recessive.
So a dog could have THREE different GENOTYPES for tail length: LL Ll ll
Both dominant = Homozygous dominant
One dominant, one recessive = Heterozygous
Both recessive = Homozygous recessive

11. Dominant and Recessive Phenotypes
But dogs could only have two different tail lengths.
Remember that a dominant allele will mask a recessive one. So for this genotype you get….
LL - long tail
Ll - long tail
ll - short tail

12. Check for Understanding (CFU)
Hair can either be straight (S) or curly (s). Caleb has two alleles for curly hair.
What is his genotype in letters? ss
What is his genotype in words?
homozygous recessive
What is his phenotype?
curly hair

13. Check for Understanding (CFU)
Forearms can either be hairy (H) or not hairy (h). Zach has two alleles for hairy forearms.
What is his genotype in letters? HH
What is his genotype in words?
Homozygous dominant
What is his phenotype?
Hairy arms – gross!

14. Check for Understanding (CFU)
Lynda has one allele for straight hair, and one allele for wavy hair. Straight hair is dominant over wavy hair.
What is her genotype in letters?
What is her genotype in words?
What is her phenotype?

15. Whiteboard Practice!
Get it!
Got it?
GOOD!
Add your direcdtions here

16. Guided Practice
The bunnies of the forests of Louisiana can either be brown or black. Brown is dominant over black.
Write all the genotypes possible for a brown bunny.

17. Guided Practice
The bunnies of the forests of Louisiana can either be brown or black. Brown is dominant to black.
What is the genotype AND phenotype of a bunny that is heterozygous?

18. Guided Practice
The bunnies of the forests of Louisiana can either be brown or black. Brown is dominant to black.
What is the genotype AND phenotype of a bunny that is homozygous recessive?

19. Guided Practice
People can have either free or attached earlobes. Free is dominant over attached.
What letters would you use to represent EACH allele?

20. Guided Practice
People can have either free or attached earlobes. Free is dominant to attached.
What is the genotype AND phenotype of someone who is homozygous dominant?

21. Guided Practice
People can have either free or attached earlobes. Free is dominant to attached.
What is the genotype AND phenotype of someone who is heterozygous?

22. Guided Practice
Chickpeas can be either green or yellow. Yellow is dominant over green.
List all the possible genotypes for a yellow chickpea.

23. Guided Practice
Chickpeas can be either green or yellow. Yellow is dominant over green.
What is genotype AND phenotype of a chickpea that is homozygous recessive? 23

24. Guided Practice
Chickpeas can be either green or yellow. Yellow is dominant over green.
What is genotype AND phenotype of a chickpea that is heterozygous? 24

25. Independent Practice (IP)
What you do not complete is homework (50% of your class grade).

26. Key Point Wrap-Up
Key Point #1: Dominant alleles mask recessive alleles.
Homozygous dominant = dominant phenotype
Homozygous recessive = recessive phenotype
Heterozygous = dominant phenotype
Key Point #2: There are three rules for abbreviating genotype
Dominant allele = capital letter
Recessive allele = lowercase letter
BOTH alleles use the same letter

27. Write in complete sentences! Don’t talk during the Exit Question!
The gene for fur color in mice has alleles for brown and white. Brown is dominant to white.
What letters are used for the each allele?
How do you know which letter to use?
Write the genotype AND phenotype for a mouse that is homozygous recessive.