RE-NEET 2024 Botany Chromosomal Disorders MCQ Question

Chapter: Principles of Inheritance and Variation

Class: 12 Biology — Chapter 5 Topic: Chromosomal Disorders / Aneuploidy Difficulty: 🟢 Easy

✅ Ans: (d) B and C only

Aneuploidy = gain or loss of one or more chromosomes, so the chromosome number is not an exact multiple of the haploid set.

• B. Addition → extra chromosome, e.g. Trisomy (2n + 1)
• C. Deletion → loss of chromosome, e.g. Monosomy (2n − 1)

❌ Substitution, translocation and inversion are structural chromosome changes; they do not by themselves change the chromosome number.

$$\boxed{\text{Aneuploidy → Addition + Deletion}}$$

📌 NCERT: Aneuploidy results from the gain or loss of one or more chromosomes, commonly due to nondisjunction during cell division. (NCERT)

🧠 NEET Trick: Aneuploidy = chromosome number changes by ±1 or more → Addition/Deletion.