Worksheet: Dihybrid Crosses - Ms. Pici's Science



Worksheet: Dihybrid CrossesU N I T 3 : G E N E T I C SSTEP 1: Determine what kind of problem you are trying to solve.STEP 2: Determine letters you will use to specify traits.STEP 3: Determine parent’s genotypes.STEP 4: Make your punnett square and make gametesSTEP 5: Complete cross and determine possible offspring.STEP 6: Determine genotypic and phenotypic ratios.Two-Factor Crosses (Di-hybrid)Ex) A tall green pea plant (TTGG) is crossed with a short white pea plant (ttgg).TT or Tt = talltt = short GG or Gg = greengg = white TG TG TG TG TtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgTtGgtgtgtgtg genotypes: all (100%) heterozygous tall, green phenotypes: all (100%) tall, green A tall green pea plant (TTGg) is crossed with a tall green pea plant (TtGg) _TTGg__ X _TtGg__TGTgTGTgGenotypes:Heterozygous tall and green: 4/16 = 1/4Heterozygous tall, homozygous green: 2/16 = 1/8Heterozygous tall, homozygous white: 2/16 = 1/8Homozygous tall and green: 2/16 = 1/8Homozygous tall, heterozygous green: 4/16 = 1/4Homozygous tall, homozygous white: 2/16 = 1/8Phenotypes:Tall, green: 12/16 = 3/4 tall, white: 4/16 = 1/4TGTTGGTTGgTTGGTTGgTgTTGgTTggTTGgTTggtGTtGGTtGgTtGGTtGgtgTtGgTtggTtGgTtgg A tall green pea plant (TtGg) is crossed with a Short white pea plant (ttgg)._TtGg_ X _ttgg_tgtgtgtgGenotypes:Heterozygous tall and green: 4/16 = 1/4Heterozygous tall, homozygous white: 4/16 = 1/4Homozygous short, heterozygous green: 4/16 = 1/4Homozygous short and white: 4/16 = 1/4Phenotypes:Tall, green: 4/16 = 1/4Tall, white: 4/16 = 1/4Short, green: 4/16 = 1/4Short, white: 4/16 = 1/4TGTtGgTtGgTtGgTtGgTgTtggTtggTtggTtggtGttGgttGgttGgttGgtgttggttggttggttgg A Homozygous tall, green (TTGG) flowered plant is crossed with a homozygous short white (ttgg) flowered plant.TTGG X ttggtgtgtgtggenotypes:all heterozygous tall and greenphenotypes: all tall and greenTGTtGgTtGgTtGgTtGgTGTtGgTtGgTtGgTtGgTGTtGgTtGgTtGgTtGgTGTtGgTtGgTtGgTtGg 4) Two Heterozygous Tall, Green pea plants are crossed.TtGg X TtGgTGTgtGtgGenotypes:Homozygous tall and green: 1/16Homozygous tall, heterozygous green: 3/16 Homozygous tall and white: 1/16Heterozygous tall and green: 3/16Heterozygous tall, homozygous green: 2/16Heterozygous tall, homozygous white: 2/16Homozygous short and green: 1/16Homozygous short and heterozygous green: 2/16Homozygous short and white: 1/16Phenotypes:Tall, green:9/16Tall, white:3/16Short, green: 3/16Short, white: 1/16TGTTGGTTGgTtGGTTGgTgTTGgTTggTtGgTtggtGTtGGTtGgttGGttGgtgTtGgTtggttGgttgg2. In man, assume that spotted skin (S) is dominant over non-spotted skin (s) and that wooly hair (W) is dominant over non-wooly hair (w). Cross a marriage between a heterozygous spotted, non-wooly man with a heterozygous wooly-haired, non-spotted woman. Give genotypic and phenotypic ratios of offspring. Ssww x ssWwS: spotteds: non-spottedW: wooly hairw: non-wooly hairSwSwswswGenotypes:Heterozygous spotted and wooly: 4/16 = 1/4Heterozygous spotted, homozygous non-wooly: 4/16 = 1/4Homozygous non-spotted, and non-wooly: 4/16 = 1/4Homozygous non-spotted, heterozygous wooly: 4/16 = 1/4Phenotypes:Spotted, wooly: 1/4Spotted, non-wooly: 1/4Non-spotted, non-wooly: 1/4Non-potted, non-wooly: 1/4sWSsWwSsWwssWwssWwsWSsWwSsWwssWwssWwswSswwSswwsswwsswwswSswwSswwsswwssww ................
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