Class 12 · Principles of Inheritance and Variation

Chromosomal Aberrations and Cancer — NEET Biology

✅ Asked in NEET 2016
✅ NEET 2016 PYQ

The mechanism that causes a gene to move from one linkage group to another is called (NEET 2016 Phase 2)

QuestionNEET 2016

The mechanism that causes a gene to move from one linkage group to another is called (NEET 2016 Phase 2)

Answer & NCERT explanation

Correct answer: C Translocation

Translocation is the mechanism that causes a gene to move from one linkage group (chromosome) to another. This involves transfer of a chromosome segment to a non-homologous chromosome. Crossing-over exchanges segments between homologous chromosomes, inversion reverses chromosome segments, and duplication creates extra copies within the same chromosome.

Read more NCERT concept on the PYQ

📖 NCERT Source

As you will learn in Chapter 5, one DNA helix runs continuously from one end to the other in each chromatid, in a highly supercoiled form. Therefore loss (deletions) or gain (insertion/duplication) of a segment of DNA, result in alteration in chromosomes. Since genes are known to be located on chromosomes, alteration in chromosomes results in abnormalities or aberrations. Chromosomal aberrations are commonly observed in cancer cells.

NCERT Biology · Class 12 · Chapter 4 · Paragraph 75
How NTA Uses This Concept

NTA tests whether students understand that deletions, insertions, and duplications of DNA segments cause chromosomal aberrations, which are frequently observed in cancer cells. The common student mistake is confusing different types of aberrations—many think deletion and insertion are the same or forget that duplication is a gain type aberration. Remember: deletions are loss of DNA segments (harmful), while insertions and duplications represent gain of DNA (also abnormal). Cancer cells commonly show these chromosomal alterations, making this a high-yield concept. Since genes sit on chromosomes, any structural change directly affects gene function and cell behavior.

❓ Frequently Asked Questions
What does NCERT say about As you will learn?
As you will learn in Chapter 5, one DNA helix runs continuously from one end to the other in each chromatid, in a highly supercoiled form. Therefore loss (deletions) or gain (insertion/duplication) of a segment of DNA, result in alteration in chromosomes.
Has this concept appeared in NEET?
Yes — appeared in NEET 2016. Mentions chromosomal alterations but translocation not explicitly defined
Which chapter is this from?
Principles of Inheritance and Variation, Class 12 NCERT Biology.

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