Mutation 🧬
What is a mutation?
A mutation happens when the DNA sequence changes, creating new versions of genes and, in turn, new traits in an organism. These changes, alongside recombination, add fresh variety to DNA and explain why individuals differ from each other. :contentReference[oaicite:0]{index=0}
How do mutations occur? 🔄
- One DNA strand in each chromatid runs continuously from end to end in a super-coiled form. When the cell loses (deletions) or gains (insertions / duplications) a DNA segment, the chromosome’s structure changes. Such chromosomal changes often show up as aberrations, a feature frequently noticed in cancer cells. :contentReference[oaicite:1]{index=1}
- A single base-pair change creates a point mutation. The textbook example is sickle-cell anemia, where one base change in the β-globin gene alters the hemoglobin protein. :contentReference[oaicite:2]{index=2}
- When base pairs are deleted or inserted in numbers not divisible by three, the reading frame shifts. These frame-shift mutations rewrite every downstream codon and usually produce a non-functional protein. :contentReference[oaicite:3]{index=3}
Mutagens — agents that trigger mutations ☢️
Certain chemicals and physical factors can push DNA to mutate; scientists call them mutagens. Ultraviolet (UV) radiation, for instance, can damage bases and spark mutations. :contentReference[oaicite:4]{index=4}
Why do mutations matter? 🎯
Because genes sit on chromosomes, any DNA change can reshape chromosomes and, by extension, affect traits. Some mutations cause disease, others fuel evolution, and still others create the variability that breeding experiments rely on. :contentReference[oaicite:5]{index=5}
High-yield ideas for NEET 🚀
- Differentiate point mutations (single-base changes) from frame-shift mutations (insertions / deletions that shift the reading frame).
- Link sickle-cell anemia to a specific point mutation in the β-globin gene.
- Connect chromosomal deletions and duplications with structural aberrations commonly seen in cancer cells.
- Recall that UV radiation acts as a physical mutagen.
