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DO NOW

DO NOW. Get out your monohybrid crosses HW A woman with a widow’s peak (heterozygous) has children with a man who does not have a widow’s peak. What is the probability they will have a child without a widow’s peak?. Dihybrid Crosses. Crosses that involve two traits

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DO NOW

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  1. DO NOW Get out your monohybrid crosses HW A woman with a widow’s peak (heterozygous) has children with a man who does not have a widow’s peak. What is the probability they will have a child without a widow’s peak?

  2. Dihybrid Crosses • Crosses that involve two traits • Similar to monohybrid crosses, but HARDER! 

  3. A pea plant that is heterozygous for round, yellow seeds is self fertilized . What are the genotypic and phenotypic ratios of the plant’s offspring?

  4. A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring? • Step 1: Write the symbols R = Round r = smooth Y = Yellow y = green

  5. A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring? • Step 2: Determine the parental genotypes and write the parental Cross.

  6. A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring? • Step 3: Determine the gametes. (kind of like the FOIL method from math class) • Combine the R’s and Y’s for each parent to determine the alleles for each egg or sperm.

  7. A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring? • Step 4: Set up a large 4x4 Punnet square, place one gamete set from parent 1 on the top and one gamete set from parent 2 on the side. Gametes – Parent #1 ry RY Ry rY RY Ry Gametes – Parent #2 rY ry

  8. A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring? • Step 5: Fill in the Punnett Square. Gametes – Parent #1 ry RY Ry rY RY RRYY RRYy RrYY RrYy RrYy Ry RRYy Rryy RRyy Gametes – Parent #2 rY RrYY RrYy rrYy rrYY ry rryy RrYy Rryy rrYy

  9. A pea plant that is heterozygous for round, yellow seeds is self fertilized. What are the genotypic and phenotypic ratios of the plant’s offspring? • Step 6: Determine the number of offspring for each phenotype (phenotypic ratio). 3 9 1 3 ___ round & yellow: ___round & green:___ wrinkled & yellow: ___ wrinkled and green Gametes – Parent #1 ry RY Ry rY RY RRYY RRYy RrYY RrYy RrYy Ry RRYy Rryy RRyy Gametes – Parent #2 rY RrYY RrYy rrYy rrYY ry rryy RrYy Rryy rrYy

  10. Dihybrid Cross

  11. Practice! • Cross a plant that is heterozygous round and heterozygous yellow with a plant that is wrinkled and green.

  12. Cross a plant that is heterozygous round and heterozygous yellow with a plant that is wrinkled and green. Parental Cross: • SYMBOLS • R = Round • r = smooth • Y = Yellow • y = green Phenotypic Ratio: 4 round & yellow 4 round & green 4 wrinkled & yellow 4 wrinkled & green 1:1:1:1

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