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Punnett Squares

Punnett Squares. Punnett Squares. A Punnett square illustrates how the parents’ alleles might combine in offspring. The top of the Punnett Square are one of the parent’s alleles, the side of the Punnett square shows the other parent’s alleles for the trait.

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Punnett Squares

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  1. Punnett Squares

  2. Punnett Squares • A Punnett square illustrates how the parents’ alleles might combine in offspring. • The top of the Punnett Square are one of the parent’s alleles, the side of the Punnett square shows the other parent’s alleles for the trait

  3. Heterozygous: having dissimilar pairs of alleles for any hereditary characteristic • Homozygous: having identical pairs of alleles for any given pair of heredity characteristics

  4. Mendel’s Laws of Inheritance • Law of Dominance: In heterozygous genotypes, dominant alleles hide recessive alleles when both are inherited by an organism. (Hh means the dominant trait will show up in the phenotype)

  5. Mendel’s Laws of Inheritance 1. The Law of Segregation (separation): Each organism has 2 alleles for a gene. Only one allele from each gene 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 • T = tall • What letters would you use to represent this cross? • 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 • Recessive trait = white hair • B = brown • b = white

  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 • Genotype % BB % Bb % bb 0 b b 50 Bb Bb B b 50 • 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 • Recessive trait = short hair • L = long • l = short

  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 • Genotype % LL % Ll % ll 50 L l 50 LL Ll L L 0 • Phenotype % long % short 100 LL Ll 0

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

  13. Ww • What is the genotype of a heterozygous wrinkly-skinned elephant? • What is the genotype of a heterozygous wrinkly-skinned elephant? • Ww • Ww x Ww • Genotype % WW % Ww % ww 25 W w 50 WW Ww W w 25 • Phenotype % 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 • Genotype % RR % Rr % rr 50 R r 50 RR Rr R R 0 • Phenotype % round % wrinkled 100 RR Rr 0

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