This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! The pedigree where an affected father and unaffected mother produce all affected daughters and unaffected sons matches X-linked dominant inheritance, as the father passes his X chromosome (with the dominant allele) to daughters (who express it) and his Y to sons (who get the mother's normal X and remain unaffected), consistent with sex-linked patterns without male-to-male transmission. Choice B correctly explains the inheritance pattern by properly interpreting the pedigree evidence to identify X-linked dominant, highlighting how fathers transmit the X to daughters and Y to sons, resulting in the observed sex-specific affection. Choice C fails because it suggests Y-linked inheritance, but Y-linked traits are passed only to sons (not daughters), and daughters do not inherit the Y chromosome, misidentifying the pattern as Y-linked when the evidence shows affected females inheriting from the father. Using evidence to determine inheritance patterns: (1) RATIO EVIDENCE: Observe offspring phenotype ratios from known or unknown parent crosses. 3:1 ratio (like 75 purple : 25 white) → dominant/recessive, heterozygous parents (Pp × Pp). 1:1 ratio (like 50 purple : 50 white) → heterozygous × homozygous recessive (Pp × pp). 1:2:1 ratio (like 25 red : 50 pink : 25 white) → incomplete dominance, heterozygous parents (RW × RW). All same phenotype → depends on parents (could be homozygous × homozygous). Ratios reveal parent genotypes and dominance patterns! (2) PUNNETT SQUARE: Use to PREDICT ratios from parent genotypes, then compare to actual data. Example: Parents both Aa → Punnett square predicts 3:1 ratio. Observed: 74 dominant, 26 recessive (close to 3:1). Match confirms model! Punnett square also determines parent genotypes from offspring: if offspring show recessive trait (aa), BOTH parents must have at least one a allele (either Aa or aa). (3) PEDIGREE PATTERNS: Trait skips generation (grandparents → grandchildren but not parents) → recessive (parents are carriers Aa, don't show trait). Trait in every generation → dominant usually. Affected parent, affected children → dominant often (one affected parent sufficient if dominant). Two unaffected parents, affected child → recessive (both parents Aa carriers). The generational pattern reveals dominance! Example full analysis: Data shows 300 purple flowers, 100 white flowers from cross (3:1 ratio). INTERPRET: 3:1 suggests dominant/recessive with heterozygous parents. INFER parent genotypes: both Pp (if P dominant for purple, p recessive for white). PREDICT: Pp × Pp should give 1 PP : 2 Pp : 1 pp = 3 purple : 1 white. CHECK: predicted 3:1 matches observed 3:1 ✓. CONCLUDE: evidence supports P dominant, p recessive, parents both heterozygous Pp. This systematic analysis uses evidence to determine inheritance pattern!

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! All 40 offspring from a purple × white cross show purple, which matches the Punnett square prediction for PP × pp producing all Pp (purple), confirming dominant/recessive with the purple parent homozygous dominant. Choice B correctly explains the inheritance pattern by properly interpreting the all-dominant offspring ratio to identify PP × pp genotypes. For example, choice A fails by suggesting Pp × pp, but that would predict a 1:1 ratio with half white offspring, not all purple as observed. Using evidence to determine inheritance patterns: (1) RATIO EVIDENCE: Observe offspring phenotype ratios from known or unknown parent crosses. 3:1 ratio (like 75 purple : 25 white) → dominant/recessive, heterozygous parents (Pp × Pp). 1:1 ratio (like 50 purple : 50 white) → heterozygous × homozygous recessive (Pp × pp). 1:2:1 ratio (like 25 red : 50 pink : 25 white) → incomplete dominance, heterozygous parents (RW × RW). All same phenotype → depends on parents (could be homozygous × homozygous). Ratios reveal parent genotypes and dominance patterns! (2) PUNNETT SQUARE: Use to PREDICT ratios from parent genotypes, then compare to actual data. Example: Parents both Aa → Punnett square predicts 3:1 ratio. Observed: 74 dominant, 26 recessive (close to 3:1). Match confirms model! Punnett square also determines parent genotypes from offspring: if offspring show recessive trait (aa), BOTH parents must have at least one a allele (either Aa or aa). (3) PEDIGREE PATTERNS: Trait skips generation (grandparents → grandchildren but not parents) → recessive (parents are carriers Aa, don't show trait). Trait in every generation → dominant usually. Affected parent, affected children → dominant often (one affected parent sufficient if dominant). Two unaffected parents, affected child → recessive (both parents Aa carriers). The generational pattern reveals dominance! Example full analysis: Data shows 300 purple flowers, 100 white flowers from cross (3:1 ratio). INTERPRET: 3:1 suggests dominant/recessive with heterozygous parents. INFER parent genotypes: both Pp (if P dominant for purple, p recessive for white). PREDICT: Pp × Pp should give 1 PP : 2 Pp : 1 pp = 3 purple : 1 white. CHECK: predicted 3:1 matches observed 3:1 ✓. CONCLUDE: evidence supports P dominant, p recessive, parents both heterozygous Pp. This systematic analysis uses evidence to determine inheritance pattern!

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! In X-linked recessive inheritance, an unaffected carrier mother $(X^E$ $X^e$) can pass the recessive $X^e$ to her son, who expresses it as $X^e$ Y since males have only one X, while the father contributes Y and can't pass an X-linked allele. Choice A correctly explains the inheritance pattern by properly interpreting the allele evidence and X-linked transmission to identify the mother's carrier status. Choice B fails because the father contributes the Y chromosome, not an X, so he can't pass the recessive X-linked allele to his son. You're grasping sex-linked patterns beautifully—keep exploring pedigrees with X-linked traits! This will deepen your understanding.

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! The presence of white (bb) offspring from two black parents means both parents must carry the recessive b allele (Bb × Bb), as a Punnett square shows this cross can produce 25% bb, while BB parents couldn't produce bb. Choice B correctly explains the inheritance pattern by properly interpreting the Punnett square evidence to identify that both parents carry the recessive allele. Choice A fails because if both were BB, no b alleles exist to produce bb offspring, contradicting the data and misapplying blending inheritance. Impressive deduction from offspring phenotypes—it's how we infer hidden genotypes! Practice more with Punnett squares to predict and verify.

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! The observed ratio of 62 tall to 18 short is approximately 3.44:1, which closely matches the 3:1 ratio expected from a Tt × Tt cross in a dominant/recessive pattern, as a Punnett square predicts 75% tall (TT or Tt) and 25% short (tt). Choice B correctly explains the inheritance pattern by properly interpreting the offspring ratios and Punnett square predictions to identify dominant/recessive inheritance with heterozygous parents. Choice A fails because it misidentifies the pattern as incomplete dominance, but the data show only two phenotypes without an intermediate form, and the ratio doesn't fit 1:2:1. Keep practicing by calculating expected ratios from Punnett squares and comparing them to observed data—it's a great way to confirm inheritance patterns! Remember, small deviations from exact ratios are common in real data due to chance, but a close match like this supports the model.

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! X-linked recessive traits show a distinctive pattern: males are affected more often than females because males have only one X chromosome (XY), so one recessive allele on their single X causes the trait. Females (XX) need two recessive alleles to be affected. Carrier mothers (XᴬXᵃ) can have affected sons (XᵃY) who inherited the recessive X from mom. This explains why unaffected mothers have affected sons. Choice B correctly identifies the key evidence for X-linked recessive inheritance—more males than females are affected because males need only one recessive allele (on their single X) while females need two. Choice A incorrectly states the trait appears in every generation, which is more typical of dominant traits; Choice C's observation doesn't distinguish X-linked from autosomal; Choice D incorrectly focuses on 3:1 ratios which aren't specific to X-linked inheritance.

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! In this case, two parents with the dominant free earlobe phenotype (E) produce a child with the recessive attached phenotype (e), which indicates the trait is recessive and both parents must be heterozygous carriers (Ee) to pass on two e alleles to the child (ee), as shown in a Punnett square for Ee × Ee predicting 25% ee. Choice B correctly explains the inheritance pattern by properly interpreting the pedigree evidence of unaffected parents producing an affected child to identify recessive inheritance with carrier parents. For example, choice C fails by misinterpreting the attached trait as dominant, but a recessive trait can appear in the child if hidden in carrier parents, not requiring dominance. Using evidence to determine inheritance patterns: (1) RATIO EVIDENCE: Observe offspring phenotype ratios from known or unknown parent crosses. 3:1 ratio (like 75 purple : 25 white) → dominant/recessive, heterozygous parents (Pp × Pp). 1:1 ratio (like 50 purple : 50 white) → heterozygous × homozygous recessive (Pp × pp). 1:2:1 ratio (like 25 red : 50 pink : 25 white) → incomplete dominance, heterozygous parents (RW × RW). All same phenotype → depends on parents (could be homozygous × homozygous). Ratios reveal parent genotypes and dominance patterns! (2) PUNNETT SQUARE: Use to PREDICT ratios from parent genotypes, then compare to actual data. Example: Parents both Aa → Punnett square predicts 3:1 ratio. Observed: 74 dominant, 26 recessive (close to 3:1). Match confirms model! Punnett square also determines parent genotypes from offspring: if offspring show recessive trait (aa), BOTH parents must have at least one a allele (either Aa or aa). (3) PEDIGREE PATTERNS: Trait skips generation (grandparents → grandchildren but not parents) → recessive (parents are carriers Aa, don't show trait). Trait in every generation → dominant usually. Affected parent, affected children → dominant often (one affected parent sufficient if dominant). Two unaffected parents, affected child → recessive (both parents Aa carriers). The generational pattern reveals dominance! Example full analysis: Data shows 300 purple flowers, 100 white flowers from cross (3:1 ratio). INTERPRET: 3:1 suggests dominant/recessive with heterozygous parents. INFER parent genotypes: both Pp (if P dominant for purple, p recessive for white). PREDICT: Pp × Pp should give 1 PP : 2 Pp : 1 pp = 3 purple : 1 white. CHECK: predicted 3:1 matches observed 3:1 ✓. CONCLUDE: evidence supports P dominant, p recessive, parents both heterozygous Pp. This systematic analysis uses evidence to determine inheritance pattern!

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! The observed 23 red, 49 pink, and 24 white offspring from two pink (RW) parents approximate a 1:2:1 phenotype ratio, which matches the Punnett square prediction for RW × RW in incomplete dominance, where pink is the intermediate heterozygote. Choice A correctly explains the inheritance pattern by properly interpreting the offspring ratios as about 1:2:1 to identify incomplete dominance. For example, choice B fails by misidentifying the ratio as 3:1 for dominant/recessive, but the three distinct phenotypes and 1:2:1 ratio do not fit that pattern. Using evidence to determine inheritance patterns: (1) RATIO EVIDENCE: Observe offspring phenotype ratios from known or unknown parent crosses. 3:1 ratio (like 75 purple : 25 white) → dominant/recessive, heterozygous parents (Pp × Pp). 1:1 ratio (like 50 purple : 50 white) → heterozygous × homozygous recessive (Pp × pp). 1:2:1 ratio (like 25 red : 50 pink : 25 white) → incomplete dominance, heterozygous parents (RW × RW). All same phenotype → depends on parents (could be homozygous × homozygous). Ratios reveal parent genotypes and dominance patterns! (2) PUNNETT SQUARE: Use to PREDICT ratios from parent genotypes, then compare to actual data. Example: Parents both Aa → Punnett square predicts 3:1 ratio. Observed: 74 dominant, 26 recessive (close to 3:1). Match confirms model! Punnett square also determines parent genotypes from offspring: if offspring show recessive trait (aa), BOTH parents must have at least one a allele (either Aa or aa). (3) PEDIGREE PATTERNS: Trait skips generation (grandparents → grandchildren but not parents) → recessive (parents are carriers Aa, don't show trait). Trait in every generation → dominant usually. Affected parent, affected children → dominant often (one affected parent sufficient if dominant). Two unaffected parents, affected child → recessive (both parents Aa carriers). The generational pattern reveals dominance! Example full analysis: Data shows 300 purple flowers, 100 white flowers from cross (3:1 ratio). INTERPRET: 3:1 suggests dominant/recessive with heterozygous parents. INFER parent genotypes: both Pp (if P dominant for purple, p recessive for white). PREDICT: Pp × Pp should give 1 PP : 2 Pp : 1 pp = 3 purple : 1 white. CHECK: predicted 3:1 matches observed 3:1 ✓. CONCLUDE: evidence supports P dominant, p recessive, parents both heterozygous Pp. This systematic analysis uses evidence to determine inheritance pattern!

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! The evidence shows two parents without attached earlobes (dominant phenotype) having a child with attached earlobes (recessive phenotype aa). For the child to be aa, they must have received one a allele from each parent. Since neither parent shows the recessive trait, both must be heterozygous carriers Aa—they show the dominant phenotype but carry the hidden recessive allele. Choice B correctly explains that the trait is recessive, both parents are likely carriers (Aa), and the child is aa—this is the classic pattern of recessive traits "skipping" a generation. Choice A incorrectly reverses the dominance relationships; Choice C incorrectly states at least one parent must be aa, but if either parent were aa they would show attached earlobes; Choice D incorrectly invokes sex-linkage when the simple recessive pattern fully explains the observation.

This question tests your ability to explain inheritance patterns using evidence from offspring ratios, Punnett squares, and pedigrees to determine whether traits follow dominant/recessive, incomplete dominance, or other inheritance patterns. Mendelian inheritance patterns can be identified from characteristic offspring ratios: DOMINANT/RECESSIVE pattern shows 3:1 phenotype ratio when two heterozygous parents cross (Aa × Aa → 1 AA : 2 Aa : 1 aa genotypes, which gives 3 dominant phenotype : 1 recessive phenotype because both AA and Aa show dominant trait while only aa shows recessive). This 3:1 ratio is evidence that one allele is dominant and one is recessive. In pedigrees, RECESSIVE traits often skip generations (two unaffected heterozygous parents Aa can have affected child aa—the recessive allele was hidden in parents but appears in child), while DOMINANT traits typically appear in every generation (can't hide—even one copy shows). INCOMPLETE DOMINANCE shows 1:2:1 phenotype ratio (matching genotype ratio) because heterozygote shows intermediate phenotype: red (RR) × white (WW) → all pink (RW), then pink × pink (RW × RW) → 1 red : 2 pink : 1 white, and the 1:2:1 ratio with intermediate phenotype is evidence for incomplete dominance rather than dominance. Recognizing which ratio or pattern appears in data allows you to determine the inheritance type! The cross of a purple-flowered plant with a white-flowered one producing all 30 purple offspring indicates the purple parent is likely homozygous dominant (PP), as a Punnett square for PP × pp predicts all Pp (purple) offspring, whereas Pp × pp would yield a 1:1 purple:white ratio, which doesn't match the uniform results. Choice B correctly explains the inheritance pattern by properly interpreting the offspring ratio evidence to identify the purple parent as PP, since the all-purple outcome from crossing with pp confirms homozygosity for the dominant allele. Choice A fails because it suggests the purple parent is Pp, but that would produce half white offspring in a test cross with pp, not the observed 100% purple, misinterpreting the ratio as supportive of heterozygosity rather than homozygosity. Using evidence to determine inheritance patterns: (1) RATIO EVIDENCE: Observe offspring phenotype ratios from known or unknown parent crosses. 3:1 ratio (like 75 purple : 25 white) → dominant/recessive, heterozygous parents (Pp × Pp). 1:1 ratio (like 50 purple : 50 white) → heterozygous × homozygous recessive (Pp × pp). 1:2:1 ratio (like 25 red : 50 pink : 25 white) → incomplete dominance, heterozygous parents (RW × RW). All same phenotype → depends on parents (could be homozygous × homozygous). Ratios reveal parent genotypes and dominance patterns! (2) PUNNETT SQUARE: Use to PREDICT ratios from parent genotypes, then compare to actual data. Example: Parents both Aa → Punnett square predicts 3:1 ratio. Observed: 74 dominant, 26 recessive (close to 3:1). Match confirms model! Punnett square also determines parent genotypes from offspring: if offspring show recessive trait (aa), BOTH parents must have at least one a allele (either Aa or aa). (3) PEDIGREE PATTERNS: Trait skips generation (grandparents → grandchildren but not parents) → recessive (parents are carriers Aa, don't show trait). Trait in every generation → dominant usually. Affected parent, affected children → dominant often (one affected parent sufficient if dominant). Two unaffected parents, affected child → recessive (both parents Aa carriers). The generational pattern reveals dominance! Example full analysis: Data shows 300 purple flowers, 100 white flowers from cross (3:1 ratio). INTERPRET: 3:1 suggests dominant/recessive with heterozygous parents. INFER parent genotypes: both Pp (if P dominant for purple, p recessive for white). PREDICT: Pp × Pp should give 1 PP : 2 Pp : 1 pp = 3 purple : 1 white. CHECK: predicted 3:1 matches observed 3:1 ✓. CONCLUDE: evidence supports P dominant, p recessive, parents both heterozygous Pp. This systematic analysis uses evidence to determine inheritance pattern!