▶️ Answer/Explanation
Answer: (C) \(Rr\) and \(Rr\)
Explanation:
Both parents have red flowers, so they must carry at least one dominant \(R\) allele. The appearance of white-flowered offspring (genotype \(rr\)) means each parent must carry a recessive \(r\) allele to pass it on. The observed phenotypic ratio in the offspring is approximately 93 red : 28 white ≈ 3.3 : 1. This is close to the 3:1 phenotypic ratio expected from a monohybrid cross between two heterozygotes (\(Rr \times Rr\)). Options A and D would not produce both phenotypes in these proportions, and option B would not yield a 3:1 ratio either. Therefore, the parents must both be heterozygous (\(Rr\)).
▶️ Answer/Explanation
Cystic fibrosis is an autosomal recessive disorder. Let $F$ represent the dominant normal allele and $f$ represent the recessive cystic fibrosis allele. Since both parents are heterozygous, their genotypes are both $Ff$. When we cross $Ff \times Ff$ using a Punnett square, the resulting offspring genotypes are $FF$ (normal), $Ff$ (carrier), $Ff$ (carrier), and $ff$ (affected). Only the homozygous recessive genotype ($ff$) results in the condition. This occurs in $1$ out of $4$ possible combinations, which equates to a probability of $25\%$.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Continuous variation refers to characteristics that show a complete range of values without distinct categories, often influenced by both multiple genes and environmental factors. Body mass in cats is a prime example because weight can be any value within a range and is affected by diet and exercise. In contrast, the other options represent discontinuous variation, where traits fall into distinct, separate categories. For instance, blood groups are strictly $A$, $B$, $AB$, or $O$, and pea seeds are either specific colors or shapes defined by clear genetic inheritance. Since body mass lacks these “steps” or fixed categories, it is classified as continuous.
✅ Answer: (B)
✅ Answer: (B)