Which of the following symbols represents mating between relatives in human pedigree analysis?
Answer: (B) A square (male) and a circle (female) joined by a double horizontal line (consanguineous mating line).. Answer: (B) A square (male) and a circle (female) joined by a double horizontal line (consanguineous mating line).
- A.A square (male) and a circle (female) joined by a single horizontal marriage/mating line.
- B.A square (male) and a circle (female) joined by a double horizontal line (consanguineous mating line).✓
- C.A square (male) and a circle (female) joined by a mating line with a vertical line descending to offspring (sibship).
- D.A filled square, a filled circle and a filled diamond (affected individuals/unknown sex symbols) on a sibship line.
Correct Answer
(B) A square (male) and a circle (female) joined by a double horizontal line (consanguineous mating line).
Solution & Explanation
Answer: (B) A square (male) and a circle (female) joined by a double horizontal line (consanguineous mating line). Solution: In standard human pedigree notation a single horizontal line connecting a square (male) and circle (female) denotes ordinary mating/marriage, whereas a DOUBLE horizontal line denotes a consanguineous mating, i.e., mating between relatives. Options (a), (c) and (d) show normal mating, a sibship/offspring line, and affected/unknown-sex symbols respectively. Hence option (b) is correct. NCERT Reference: NCERT Class XII, Ch 4, p.72, lines 44-45: "Some of the important standard symbols used in the pedigree analysis have been shown in Figure 4.13." (the double-line consanguineous-mating symbol is part of the standard pedigree symbol set in Figure 4.13; specific double-line meaning is conventional pedigree notation extending this figure).