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Biology

Biology. Genetics Test crosses & Pedigrees. What is a Testcross?. Method used to determine an unknown organisms genotype Involves crossing an unknown organism with a homozygous recessive

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Biology

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  1. Biology Genetics Test crosses & Pedigrees

  2. What is a Testcross? • Method used to determine an unknown organisms genotype • Involves crossing an unknown organism with a homozygous recessive • If any of the offspring are recessive, then the unknown parent had to carry recessive traits so was heterozygous.

  3. What is a pedigree? • Pedigrees: graphic representation of family tree • May be used if testcross cannot be made • Pedigree key: • = male • = female • = marriage • Children = connected to marriage by vertical life • = recessive male/female (bb) • = heterozygous ½ shaded, ½ unshaded

  4. Suppose in dogs, Long tongue (L) is dominant over short (l) and Short hair (H) is dominant over long hair (h). What gene combinations could be found in a dog that is LLHh? • LH, Lh • LH, lH, lh, Lh • LH only • In pea plants, round seeds (R) are dominant to wrinkled (r) and yellow seeds (Y) are dominant to green seeds (y). What is the phenotype of the box labeled A? (Hint: figure out the genotype first then phenotype.) a. Round, yellow b. Round, green c. Wrinkled, green A

  5. What relationship exists between Jim & Kay? • They are brother and sister • They are married • Jim is Kay’s uncle • What does a shaded circle represent? a. Female with a disease/disorder b. Female without a disease/disorder • What is Joe’s genotype? a. BB b. Bb c. bb • What must Tom’s genotype be? (Hint: Look at the genotypes of his two sons) • BB b. Bb c. bb

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