▶️ Answer/Explanation
To determine the mode of inheritance, look at the parents in the second generation who both have the condition. They produce an unaffected daughter. If the condition were recessive, two affected parents (genotype $aa$) could only produce affected offspring ($aa$). Because they produced an unaffected child, the parents must be heterozygous ($Aa$) and the condition must be dominant. The unaffected daughter inherited the recessive “normal” allele from each parent ($aa$). Additionally, it is not necessarily sex-linked because an affected father has an unaffected daughter, which is possible in autosomal dominant inheritance.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Since the disease is sex-linked recessive, males ($XY$) cannot be heterozygous; they are either affected or unaffected. Individual $4$ is an affected male, meaning he inherited the recessive allele from his mother, individual $2$. Since individual $2$ is unaffected but has an affected son, she must be a carrier ($X^RX^r$), making her heterozygous. Similarly, individual $3$ is an unaffected female who has an affected son (individual $5$). To pass the recessive allele to her son, individual $3$ must also be a carrier ($X^RX^r$). Individual $1$ is an unaffected male ($X^RY$) and therefore cannot be heterozygous.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
An adaptive feature is an inherited functional, structural, or behavioral trait that increases an organism’s fitness within its specific habitat. These traits are the result of natural selection, ensuring that individuals better suited to their surroundings are more likely to reach reproductive age. While a phenotype describes any observable trait, not all phenotypes are necessarily helpful for survival. Competition is a process between organisms, and an observable feature is a general term that lacks the specific context of evolutionary advantage. Therefore, “adaptive feature” is the most precise biological term for a trait that actively aids survival and reproduction.
✅ Answer: (A)
✅ Answer: (A)