1. Dominant, Recessive, Heterozygous, Homozygous  Catalyst:  Toby has a deep voice. Is this genotype or phenotype? HOW DO YOU KNOW?  Paula has one allele for being tall, and one allele for being short. Is this genotype or phenotype? HOW DO YOU KNOW? Write in complete sentences! Don’t talk during the Catalyst!

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

3. Agenda  Quick review: genotype and phenotype  Principal of Dominance  Abbreviating Genotypes and Phenotypes  Concept Map  Practice  Pre-Test  Exit Question

4. Quick Review  All living organisms have two alleles for every gene  Gene controls one trait  Allele = version of a gene  Genotype = which alleles you got from parents  Phenotype = physical expression of the genotype

5. Principle of Dominance  Key Point #1: Dominant alleles mask recessive alleles.  Dominant alleles make it like the recessive allele isn’t there Two dominant alleles = dominant phenotype Two recessive alleles = recessive phenotype One of each = dominant phenotype

6. Principle of Dominance  Example: hair color (gene). The brown allele is dominant, the blonde allele is recessive  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 (CFU)  Long fingers are dominant, short fingers are recessive  Asia has two dominant alleles  What type of fingers does she have?

8. Check for Understanding (CFU)  Long fingers are dominant, short fingers are recessive  Tonya has one dominant allele and one recessive allele  What type of fingers does she have?

9. Check for Understanding (CFU)  Long fingers are dominant, short fingers are recessive  Brice has two recessive alleles  What type of fingers does he have?

10. Check for Understanding (CFU)  Long fingers are dominant, short fingers are recessive  Jaron has one dominant allele and one recessive allele  What type of fingers does he have?

11. But Mr. LY, I’m Lazy!  Key Point #2: There are three rules for abbreviating genotype 1. Dominant allele = capital letter 2. Recessive allele = lowercase letter 3. BOTH alleles use the same letter  Long tails in dogs are dominant, short tails are recessive  Long = L  Short = l

12. 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 Both recessive = Homozygous recessive One dominant, one recessive = Heterozygous

13. 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)

14. 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?  What is his genotype in words?  What is his phenotype?

15. 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?  What is his genotype in words?  What is his phenotype?

16. 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?

17. two types WORD BANK: allele, dominant (3x), homozygous recessive, recessive (2x), homozygous dominant, heterozygous two of this kind one of each looks

18. Whiteboard Practice!

19. 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.

20. 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?

21. 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?

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

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

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

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

26. 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?

27. 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?

28. Independent Practice (IP)

29. 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 1. Dominant allele = capital letter 2. Recessive allele = lowercase letter 3. BOTH alleles use the same letter

30. Pre-test

31. 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 alleles?  Write the genotype AND phenotype for a mouse that is homozygous recessive. Write in complete sentences! Don’t talk during the Exit Question!