NCERT Class 11 Biotechnology Biotechnology: Chapter 8 — Chromosomal Abnormalities and Syndromes
Chapter 8 of NCERT Class 11 Biotechnology, titled "Chromosomal Abnormalities and Syndromes," delves into the changes that can occur in chromosomes, affecting genetic makeup and leading to various conditions. It explains that environmental factors like radiation or internal genetic issues can cause damage or numerical changes in chromosomes. Structural abnormalities include deletion, duplication, inversion, and translocation, where segments of chromosomes are lost, repeated, reversed, or moved to different chromosomes, respectively. Numerical abnormalities involve changes in chromosome number, such as monosomy (one chromosome missing) and trisomy (an extra chromosome), which fall under aneuploidy. Polyploidy, the multiplication of entire chromosome sets, is also discussed, highlighting its role in plant breeding with examples like hexaploid bread wheat and triploid bananas. These chromosomal alterations can significantly impact phenotypic traits, resulting in diseases and syndromes, and are crucial for understanding genetic disorders and their inheritance patterns in biology.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Biotechnology |
| Book | Biotechnology |
| Chapter | Chapter 8 — Chromosomal Abnormalities and Syndromes |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 3 minutes |
| Word count | 438 |
Learning outcomes
- Differentiate between structural and numerical chromosomal abnormalities.
- Define and provide examples of deletion, duplication, inversion, and translocation.
- Explain monosomy, trisomy, aneuploidy, and polyploidy.
- Understand the role of chromosomal abnormalities in causing genetic disorders and syndromes.
- Recognize the significance of polyploidy in plant breeding.
Vocabulary
| Word | Meaning |
|---|---|
| Aneuploidy | Abnormal number of chromosomes in a cell. |
| Monosomy | Condition where one chromosome of a pair is absent (2n-1). |
| Trisomy | Condition where a chromosome is present in three copies (2n+1). |
| Polyploidy | Condition where the entire set of chromosomes is multiplied. |
| Deletion | Loss of a segment of a chromosome. |
| Duplication | Repetition of a segment of a chromosome. |
| Inversion | A segment of a chromosome breaks, reverses, and reattaches. |
| Translocation | A segment of a chromosome breaks and reattaches to another chromosome. |
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Practice questions
- What is the difference between aneuploidy and polyploidy? Answer: Aneuploidy involves an abnormal number of individual chromosomes, while polyploidy involves the multiplication of entire sets of chromosomes.
- Give an example of a structural chromosomal abnormality. Answer: Deletion, duplication, inversion, or translocation are examples of structural chromosomal abnormalities.
- What is trisomy? Answer: Trisomy is a condition where a chromosome is present in three copies instead of the usual two (2n+1).
- How can environmental factors affect chromosomes? Answer: Environmental factors like radiation can cause damage or changes in chromosome structure or number.
Frequently asked questions
What are the main types of chromosomal abnormalities?
Chromosomal abnormalities are broadly classified into structural abnormalities (deletion, duplication, inversion, translocation) and numerical abnormalities (monosomy, trisomy, polyploidy).
What is the difference between monosomy and trisomy?
Monosomy is the absence of one chromosome from a pair (2n-1), while trisomy is the presence of an extra chromosome, making it three in a set (2n+1).
What is aneuploidy?
Aneuploidy is a condition where the chromosome number deviates from the normal diploid number by less than a complete set, such as monosomy or trisomy.
What is polyploidy?
Polyploidy is a condition where an organism has more than two complete sets of chromosomes, like triploid (3n) or hexaploid (6n).
Can environmental factors cause chromosomal abnormalities?
Yes, environmental factors such as radiation, certain food intakes, or internal genetic conditions can lead to chromosomal damage or changes in number.
Give examples of polyploid varieties used in food.
Examples include bread wheat (hexaploid), cabbages/mustards (tetraploids), banana and apple (triploids), and strawberry and sugar cane (octoploids).
Related resources
Important topics
Topics covered
NCERT Class 11 Biotechnology — Biotechnology — Chapter 8 — Chromosomal Abnormalities and Syndromes. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.