Mutations and Biotechnology

By the end of this lesson, you will be able to classify types of mutations, evaluate their consequences, describe key biotechnology techniques (PCR, gel electrophoresis, CRISPR, recombinant DNA), and discuss ethical implications.

Mutations

A mutation is any change in the DNA sequence.

Gene Mutations (Point Mutations)

Substitution: one base replaced by another.

• Synonymous (silent): same amino acid
• Missense: different amino acid → altered protein
• Nonsense: new stop codon → truncated protein

Insertion or deletion: one or more bases added or removed.

• Frameshift mutation: shifts the reading frame for all downstream codons → usually severe

Chromosomal Mutations

• Deletion: segment removed
• Duplication: segment copied an extra time
• Inversion: segment reversed
• Translocation: segment moves to a different chromosome

Example: Philadelphia chromosome (translocation of chromosomes 9 and 22) → chronic myelogenous leukemia.

Causes of Mutations

Mutagens: agents that increase mutation rate.

• Physical: UV radiation (pyrimidine dimers in DNA), X-rays (strand breaks)
• Chemical: tobacco carcinogens, aflatoxin, nitrous acid
• Biological: some viruses insert DNA into host genome

Spontaneous mutations: from DNA replication errors that escape proofreading.

Biotechnology Techniques

PCR (Polymerase Chain Reaction)

Purpose: amplify specific DNA sequences (make millions of copies from trace amounts).

Process: denature (heat) → anneal primers (cool) → extend (DNA polymerase builds) → repeat ~30 cycles → ~10⁹ copies.

Applications: forensic DNA analysis, COVID tests, paternity testing, gene cloning.

Gel Electrophoresis

Purpose: separate DNA fragments by size.

Process: DNA loaded in wells; electric field applied; smaller fragments travel farther; stained and visualized under UV.

Applications: DNA fingerprinting, verifying PCR products, RFLP analysis.

CRISPR-Cas9

Purpose: precise gene editing — cut and modify specific DNA sequences.