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Punnett Squares

Punnett Squares. Punnett Squares. I llustrates how the parents ’ alleles might combine in offspring. One parent’s alleles are placed down the side of the square, the other parent’s alleles are placed along the top. Heterozygous : having different alleles for a hereditary character

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Punnett Squares

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  1. Punnett Squares

  2. Punnett Squares • Illustrates how the parents’ alleles might combine in offspring. • One parent’s alleles are placed down the side of the square, the other parent’s alleles are placed along the top

  3. Heterozygous: having different alleles for a hereditary character • Homozygous: having identical alleles for a heredity character

  4. Mendel’s Laws of Inheritance • Law of Dominance: In heterozygous genotypes, dominant alleles “hide” recessive alleles when both are inherited by an organism.

  5. Mendel’s Laws of Inheritance 1. The Law of Segregation (separation): Each organism has 2 alleles for a trait. Only one allele from each pair will be passed on to the offspring.

  6. Homozygous/Heterozygous Hmzg / Htzg • Cross a homozygous dominant tall plant with a homozygous recessive short plant. • Dominant trait = tall • Recessive trait = short • What letters would you use to represent this cross? • T = tall • t = short

  7. TT • What is the genotype of a homozygous recessive short plant? • What is the genotype of a homozygous dominant tall plant? • tt • TT x tt • Genotype % TT % Tt % tt 0 t t 100 Tt Tt T T 0 • Phenotype % tall % short 100 Tt Tt 0

  8. What letters would you use to represent this cross? 2. Cross a heterozygous brown haired rabbit with a homozygous recessive white haired rabbit. • Dominant trait = brown hair (B) • Recessive trait = white (b)

  9. Bb • What is the genotype of a homozygous recessive white haired rabbit? • What is the genotype of a heterozygous brown haired rabbit? • bb • Bb x bb • Possible Genotype(s) % BB % Bb % bb 0 b b 50 Bb Bb B b 50 • Possible Phenotype % brown % white 50 bb bb 50

  10. 3.. Cross a homozygous dominant long haired guinea pig with a heterozygous long haired guinea pig. What letters would you use to represent this cross? • Dominant trait = long hair (L) • Recessive trait = short hair (l)

  11. LL • What is the genotype of a heterozygous long haired guinea pig? • What is the genotype of a homozygous dominant long haired guinea pig? • Ll • LL x Ll • Possible Genotype(s) % LL % Ll % ll 50 L l 50 LL Ll L L 0 • Possible Phenotype(s) % long % short 100 LL Ll 0

  12. 4. Cross a heterozygous wrinkly elephant with another heterozygous wrinkly elephant. • Dominant trait = wrinkly skin (W) What letters would you use to represent this cross? • Recessive trait = smooth skin (w)

  13. Ww • What is the genotype of a heterozygous elephant? • What is the genotype of a heterozygous elephant? • Ww • Ww x Ww • Possible Genotype(s) % WW % Ww % ww 25 W w 50 WW Ww W w 25 • Possible Phenotype(s) % wrinkly % smooth 75 Ww ww 25

  14. A plant that is homozygous dominant for round seeds is crossed with a heterozygous plant. What is the probability that the offspring will have wrinkled seeds? • R = round • r = wrinkled RR x Rr • Possible Genotype(s) % RR % Rr % rr 50 R r 50 RR Rr R R 0 • Possible Phenotype(s) % round % wrinkled RR Rr 100 0

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