Genetics worksheet featuring pedigree charts and questions on inheritance patterns.
Genetic Pedigree Worksheet with family tree diagrams and genetic inheritance questions.
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Step-by-step solution for: pedigree practice answers - Name Date Period: Genetics Pedigree ...
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Show Answer Key & Explanations
Step-by-step solution for: pedigree practice answers - Name Date Period: Genetics Pedigree ...
1. a) Autosomal recessive
b) Individual II-3 is affected, but neither parent (I-1 and I-2) is affected → autosomal recessive inheritance pattern.
c) 1/4
d) 0% — individual III-2 is unaffected; since the trait is recessive, he must be either homozygous dominant or heterozygous, but cannot be homozygous recessive.
2. a) Autosomal dominant
b) Individual I-1 is affected and passes the trait to offspring; both males and females are affected across generations → autosomal dominant.
c) 50% — individual II-4 is affected (heterozygous, assuming penetrance), so each child has 50% chance of inheriting the mutant allele.
d) 100% — individual III-3 is affected; if the trait is autosomal dominant and she inherited it from her father (II-4), then her genotype must include the dominant allele.
3. a) X-linked recessive
b) More males are affected; affected males inherit from carrier mothers; no male-to-male transmission → X-linked recessive.
c) 50% — individual II-2 is a carrier (X^A X^a), so each son has 50% chance of being affected (X^a Y).
d) 0% — individual III-1 is male and unaffected; since the trait is X-linked recessive, he must have inherited the normal X from his mother (II-2).
4. a) Autosomal recessive
b) Affected individuals appear in multiple generations; both sexes affected equally; unaffected parents can have affected children → autosomal recessive.
c) 25% — both parents (II-3 and II-4) are carriers (Aa), so probability of affected child (aa) is 1/4.
d) 66.7% — individual III-2 is unaffected; given that both parents are carriers, the possible genotypes for an unaffected child are AA (1/3) or Aa (2/3), so probability of being a carrier is 2/3 ≈ 66.7%.
5. a) X-linked dominant
b) Affected females pass trait to ~50% of offspring; affected males pass trait to all daughters but no sons → X-linked dominant.
c) 50% — individual II-1 is affected female (X^A X^a), so each child has 50% chance of inheriting the mutant allele.
d) 100% — individual III-1 is affected male; since the trait is X-linked dominant, he must have inherited the mutant X from his mother (II-1).
6. a) Autosomal dominant
b) Trait appears in every generation; affected individuals have at least one affected parent; both sexes affected → autosomal dominant.
c) 50% — individual II-3 is affected (assumed heterozygous), so each child has 50% chance of inheriting the mutant allele.
d) 100% — individual III-2 is affected; since the trait is autosomal dominant, she must carry the mutant allele.
7. a) X-linked recessive
b) Affected males; carrier females; no male-to-male transmission → X-linked recessive.
c) 50% — individual II-2 is a carrier (X^A X^a); each son has 50% chance of being affected (X^a Y).
d) 0% — individual III-1 is male and unaffected; must have inherited normal X from mother (II-2).
8. a) Autosomal recessive
b) Affected individuals born to unaffected parents; skips generations; equal sex distribution → autosomal recessive.
c) 25% — both parents (II-2 and II-3) are carriers (Aa), so probability of affected child (aa) is 1/4.
d) 66.7% — individual III-1 is unaffected; given carrier parents, probability of being carrier (Aa) is 2/3 ≈ 66.7%.
b) Individual II-3 is affected, but neither parent (I-1 and I-2) is affected → autosomal recessive inheritance pattern.
c) 1/4
d) 0% — individual III-2 is unaffected; since the trait is recessive, he must be either homozygous dominant or heterozygous, but cannot be homozygous recessive.
2. a) Autosomal dominant
b) Individual I-1 is affected and passes the trait to offspring; both males and females are affected across generations → autosomal dominant.
c) 50% — individual II-4 is affected (heterozygous, assuming penetrance), so each child has 50% chance of inheriting the mutant allele.
d) 100% — individual III-3 is affected; if the trait is autosomal dominant and she inherited it from her father (II-4), then her genotype must include the dominant allele.
3. a) X-linked recessive
b) More males are affected; affected males inherit from carrier mothers; no male-to-male transmission → X-linked recessive.
c) 50% — individual II-2 is a carrier (X^A X^a), so each son has 50% chance of being affected (X^a Y).
d) 0% — individual III-1 is male and unaffected; since the trait is X-linked recessive, he must have inherited the normal X from his mother (II-2).
4. a) Autosomal recessive
b) Affected individuals appear in multiple generations; both sexes affected equally; unaffected parents can have affected children → autosomal recessive.
c) 25% — both parents (II-3 and II-4) are carriers (Aa), so probability of affected child (aa) is 1/4.
d) 66.7% — individual III-2 is unaffected; given that both parents are carriers, the possible genotypes for an unaffected child are AA (1/3) or Aa (2/3), so probability of being a carrier is 2/3 ≈ 66.7%.
5. a) X-linked dominant
b) Affected females pass trait to ~50% of offspring; affected males pass trait to all daughters but no sons → X-linked dominant.
c) 50% — individual II-1 is affected female (X^A X^a), so each child has 50% chance of inheriting the mutant allele.
d) 100% — individual III-1 is affected male; since the trait is X-linked dominant, he must have inherited the mutant X from his mother (II-1).
6. a) Autosomal dominant
b) Trait appears in every generation; affected individuals have at least one affected parent; both sexes affected → autosomal dominant.
c) 50% — individual II-3 is affected (assumed heterozygous), so each child has 50% chance of inheriting the mutant allele.
d) 100% — individual III-2 is affected; since the trait is autosomal dominant, she must carry the mutant allele.
7. a) X-linked recessive
b) Affected males; carrier females; no male-to-male transmission → X-linked recessive.
c) 50% — individual II-2 is a carrier (X^A X^a); each son has 50% chance of being affected (X^a Y).
d) 0% — individual III-1 is male and unaffected; must have inherited normal X from mother (II-2).
8. a) Autosomal recessive
b) Affected individuals born to unaffected parents; skips generations; equal sex distribution → autosomal recessive.
c) 25% — both parents (II-2 and II-3) are carriers (Aa), so probability of affected child (aa) is 1/4.
d) 66.7% — individual III-1 is unaffected; given carrier parents, probability of being carrier (Aa) is 2/3 ≈ 66.7%.
Parent Tip: Review the logic above to help your child master the concept of genetics pedigree worksheet.
