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Dihybrid Punnett Squares

Dihybrid Punnett Squares. You are a product of your family and your environment. Review: Monohybrid Cros. Autosomal Dominant/Recessive inheritance Predicting one trait at a time Mono=one. Dihybrid Worksheet. Autosomal Dominant/Recessive Inheritance Dealing with two traits at a time

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Dihybrid Punnett Squares

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  1. Dihybrid Punnett Squares You are a product of your family and your environment.

  2. Review: Monohybrid Cros • Autosomal Dominant/Recessive inheritance • Predicting one trait at a time • Mono=one

  3. Dihybrid Worksheet • Autosomal Dominant/Recessive Inheritance • Dealing with two traits at a time • Di-hybrid(“di”= two) • Diagram to right: • Round vs wrinkled • Green vs yellow

  4. Hair color H=dark hair h= light hair Eye Color B=Brown b=blue Two phenotypic traits

  5. Mendel’s Law of Independent Assortment • Traits are caused by genes on different chromosomes • Ex. Gg Yy • Can form sperm or eggs that are GY, Gy, gY, or gy • Sorting of DNA into gametes is random of other chromosomes

  6. What type of gametes? • Person homozygous for dark hair and dark eyes • Genotype: HHBB • Gametes: only HB HH BB HB HB HB HB

  7. Heterozygous for one trait • What about a person heterozygous for dark hair and homozygous dominant for eye color • Genotype: HhBB • Gametes: HB or hB Hh BB hB HB HB hB

  8. Heterozygous for both traits • What gametes will a person heterozygous for both traits produce? • Genotype: HhBb • Gametes: HB, Hb, hB, hb Hh Bb hB HB Hb hb

  9. Dihybrid Worksheet Step 1 • Step 1: Determine genotypes of both parents • One parent is homozygous dominant for both traits … • Genotype: HHBB • …other parent is heterozygous for both traits. • Genotype: HhBb

  10. Step 2: List all possible gametes • Parent 1 genotype: HHBB • HB • Parent 2 genotype: HhBb • HB • Hb • hB • Hb • Your punnett square will be one by four squares long

  11. Step 3: Draw punnett squares • Dimensions depend on parent’s gametes • No longer simply two by two • Parent’s gametes are 1 and 4 so punnett square will be 1 by 4

  12. Step 4: • Take one parent and list possible gametes on appropiate side • Parent one had 1 possible gamete production(HB) HB

  13. Step 5 • Take other parent and list possible gametes along punnett squares • Parent 2 has 4 possible gametes(HB, Hb, hB, hb) HB Hb hB hb HB

  14. Step 6 • Carry out punnett squares and fill them in • Dihybrid is two traits: four alleles HB Hb hB hb HHBB HHBb HhBB HhBb HB

  15. Step 7 • Write genotype ratios • Genotype:1 HHBB:1HHBb:1HhBB:1 HhBb HB Hb hB hb HHBB HHBb HhBB HhBb HB

  16. Step 7 • Write the phenotype ratios • F1 phenotype: All dark hair/brown eyes HB Hb hB hb HHBB HHBb HhBB HhBb HB

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