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Dihybrid Cross

Dihybrid Cross. Dihybrid Cross. When two pairs of contrasting characters are compared at the same time. . Dihybrid Cross. When two pairs of contrasting characters are compared at the same time. EG – Mendel crossed 2 parents differing in seed shape and seed colour. . Dihybrid Cross.

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Dihybrid Cross

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  1. Dihybrid Cross

  2. Dihybrid Cross • When two pairs of contrasting characters are compared at the same time.

  3. Dihybrid Cross • When two pairs of contrasting characters are compared at the same time. • EG – Mendel crossed 2 parents differing in seed shape and seed colour.

  4. Dihybrid Cross • When two pairs of contrasting characters are compared at the same time. • EG – Mendel crossed 2 parents differing in seed shape and seed colour. • 1 parent was true-breeding for round, yellow seeds, and the other was true-breeding for wrinkled, green seeds.

  5. Dihybrid Cross • When two pairs of contrasting characters are compared at the same time. • EG – Mendel crossed 2 parents differing in seed shape and seed colour. • 1 parent was true-breeding for round, yellow seeds, and the other was true-breeding for wrinkled, green seeds. • All the F1 seeds were round and yellow – this proves that these were the dominant traits

  6. Dihybrid Cross • RRYY x rryy Round, yellow Wrinkled, green RY RYryry RrYy (F1) Heterozygous, round, yellow

  7. Dihybrid Cross RrYyRrYy Heterozygous, Heterozygous, Yellow, round Yellow, round (male) (female) RY RyryrYRYRyryrY **put this into a punnet square

  8. Dihybrid Cross

  9. Dihybrid Cross • What is the percentage of yellow? • What is the percentage of green? • What is the percentage of wrinkled? • What is the percentage of round? • What is the percentage of round & yellow? • What is the percentage of round & green? • What is the percentage of wrinkled & yellow? • What is the percentage of wrinkled & green?

  10. Dihybrid Cross • Mendel (was very clever) predicted that ¾ of the F2 would be round, and ¼ would be wrinkled

  11. Dihybrid Cross • Mendel (was very clever) predicted that ¾ of the F2 would be round, and ¼ would be wrinkled • (9/16 + 3/16 = 12/16 or ¾) • (3/16 + 1/16 = 4/16 or ¼)

  12. Dihybrid Cross • Mendel (was very clever) predicted that ¾ of the F2 would be round, and ¼ would be wrinkled • (9/16 + 3/16 = 12/16 or ¾) • (3/16 + 1/16 = 4/16 or ¼) • He also predicted that ¾ would be yellow, and ¼ would be green • (same percentages)

  13. Dihybrid Cross • Mendel (was very clever) predicted that ¾ of the F2 would be round, and ¼ would be wrinkled • (9/16 + 3/16 = 12/16 or ¾) • (3/16 + 1/16 = 4/16 or ¼) • He also predicted that ¾ would be yellow, and ¼ would be green • (same percentages) • This means there is a 3:1 ratio for shape and a 3:1 ration for colour.

  14. Dihybrid Cross • We have to remember that these two ratios are INDEPENDENT of eachother – this means that if we pick a seed at random, there is a ¾ chance of it being round and a ¾ chance that it will be yellow.

  15. Dihybrid Cross • We have to remember that these two ratios are INDEPENDENT of eachother – this means that if we pick a seed at random, there is a ¾ chance of it being round and a ¾ chance that it will be yellow. • For us to get a yellow AND round seed is ¾ X ¾ = 9/16

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