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Phenotype & Genotype

Phenotype & Genotype. Phenotype is the ___________________ an organism has because of the alleles it has. Examples: brown fur, white flowers, dwarfism, blue eyes, etc… Genotype is the ________________ an organism has, represented by letters Examples: Bb, pp, Dd , bb, etc…

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Phenotype & Genotype

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  1. Phenotype & Genotype • Phenotype is the ___________________ an organism has because of the alleles it has. • Examples: brown fur, white flowers, dwarfism, blue eyes, etc… • Genotype is the ________________ an organism has, represented by letters • Examples: Bb, pp, Dd, bb, etc… • What is the phenotype of the rat in the do now? • What is it’s genotype?

  2. Heterozygous & Homozygous • The genotype of an organism can be heterozygous or homozygous • Heterozygous individuals have two __________ alleles for a gene – like the rat in the do now. (Hetero = different) • Example: Bb = one brown eye allele, one blue eye allele • Homozygous individuals have two of the _________ allele. (Homo = same) • Example: BB, bb, PP, pp, etc…

  3. Dominant & Recessive alleles: The relationship of Genotype & Phenotype • Since a homozygous individual has two identical alleles, their phenotype will be whatever those alleles are • Genotype = BB; Phenotype = brown eyes • Genotype = bb; Phenotype = blue eyes • A heterozygous individual will have the ______________ trait. • A dominant allele is on that ________________________ the presence of a recessive one. • Genotype = Bb; Phenotype = brown eyes • Brown eye allele (B) is dominant to blue eye allele (b)

  4. Practice • In cows, having spots (S) is dominant to no spots (s) • What is the phenotype of a cow that has spots? • What is the genotype of a heterozygous cow? • Will a heterozygous cow have spots? • What is the genotype of a cow with no spots? • If a cow has spots, what 2 genotypes might it have?

  5. More Practice • In pea plants, yellow seed color (Y) is dominant to green seed color (y). • What is the genotype of a plant with green seeds? • What is the phenotype of a Yy plant? • Is a YY plant homozygous or heterozygous? • Is a yy plant homozygous or heterozygous? • If a YY plant self-fertilizes, what color will the seeds of its offspring be?

  6. Type of Inheritance #1: Autosomal Dominance • If a gene is autosomal dominant: • The gene is located on an _____________, so all diploids have ____ copies. • One allele is dominant to the recessive version, giving homozygous dominant and heterozygous individuals the same phenotype • Example: tongue rolling in humans • TT = • Tt = • tt =

  7. Punnett Square • A diagram that helps ____________________of a genetic cross. • The offspring produced by a genetic cross are described in two ways: • Phenotype ratio: the ratio of one phenotype to the other. • Example: 2 black rats, 2 white rats = 1:1 phenotype ratio • Genotype ratio: the ratio of all of the different genotypes of the offspring • Example: 1 BB, 2 Bb, 1 bb = 1:2:1 genotype ratio

  8. Monohybrid Cross • Step 1: draw a 2 x 2 square • Step 2: put the possible alleles from parent number one on top of the two squares • Step 3: put the possible alleles from parent number 2 on the left • Step 4: Write the alleles at top down the column, and the alleles at left across the row • Step 5: Check

  9. Genetic Crosses

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