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Dominant, Recessive, Heterozygous, Homozygous Catalyst: Cedric has a deep voice. 1. Is this genotype or phenotype? HOW DO YOU KNOW? Paula has one allele for being tall, and one allele for being short. 2. Write in complete sentences! Don’t talk during the Catalyst! HW ON DESK! Is this genotype or phenotype? MASTERY TRACKER IN FOLDER! HOW DO YOU KNOW? Objectives By the end of today, all SWBAT… Differentiate between homozygous and heterozygous genotypes Determine the phenotype of an organism, based on its genotype Agenda Genotype and phenotype review Principal of Dominance Abbreviating Genotypes and Phenotypes Practice Exit Question Remember yesterday? Genes: Pieces of DNA you inherit from parents. Alleles: Different versions of genes. Genotype Combination of alleles inherited from parents In your GENES Phenotype PHYSICAL showing of your genes “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 Principle of Dominance example GENE: Hair color Dominant: Brown Alex Recessive: Blonde 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!!! Check for Understanding (CFU) Long fingers are dominant, short fingers are recessive. Asia has two dominant alleles. What type of fingers does she have? 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? Check for Understanding (CFU) Long fingers are dominant, short fingers are recessive. Brice has two recessive alleles. What type of fingers does he have? 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? But Ms. S, I’m Lazy! Key Point #2: There are three rules for abbreviating genotype 1. 2. 3. 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 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 One dominant, onedominant recessive = = Both recessive Heterozygous Homozygous recessive 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 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 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 What dominant is his phenotype? Hairy arms – gross! 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? Whiteboard Practice! Get it! Got it? GOOD! 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. 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? 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? Guided Practice People can have either free or attached earlobes. Free is dominant over attached. What letters would you use to represent EACH allele? 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? 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? Guided Practice Chickpeas can be either green or yellow. Yellow is dominant over green. List all the possible genotypes for a yellow chickpea. 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? 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? Independent Practice (IP) Front of worksheet. (COMPLETE SENTENCES!) Back of worksheet is homework. (Does not have to be in complete sentences – but the assignment has to be complete for credit.) 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. 2. 3. Dominant allele = capital letter Recessive allele = lowercase letter BOTH alleles use the same letter Exit Question 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 alleles? Write the genotype AND phenotype for a mouse that is homozygous recessive.