Biotechnology and mutation — gels, PCR, transformation and mutation types

Gel electrophoresis, PCR and bacterial transformation turn up on the AP Biology exam year after year, usually as data to interpret rather than as facts to recite: which band belongs to which fragment, which suspect matches a sample, which bacteria will grow on which plate. Mutation questions are similar: you are given a codon change or a shifted sequence and asked what kind of mutation it is and what it does to the protein. This material trains that interpretation, together with the replication mechanics that Unit 6 expects you to know.

The replication questions start from the classic density-label experiment with heavy and light nitrogen and ask what semiconservative replication predicts after one round. Others check the roles of the enzymes the course names — helicase, topoisomerase, DNA polymerase and ligase — the need for an RNA primer, and synthesis in the 5' to 3' direction.

The mutation questions give the actual codons: a substitution that swaps one amino acid for another, a substitution that turns a tyrosine codon into a stop codon, and a single-nucleotide deletion whose effect you trace codon by codon to see the reading frame shift. A bacterial scenario asks you to tell transduction apart from conjugation and transformation when a resistance gene reaches new cells inside phage particles, with no contact between cells.

The biotechnology questions are written as results you read in words. You place fragments of 800, 1,700 and 2,500 base pairs on a gel and explain why DNA runs toward the positive electrode and why small fragments run farthest; match a crime-scene DNA profile to one of three suspects; calculate how many copies PCR makes from one molecule after six cycles; identify what happens at each temperature of a PCR cycle; and predict which bacteria survive on an antibiotic plate after transformation with a resistance plasmid.

The material offers a quiz and a flashcard deck. The quiz explanations name the reasoning behind each result — why a band sits where it does, why a mutation is nonsense rather than missense — so you can apply it to a new gel or sequence on exam day. The sixteen flashcards cover replication enzymes, mutation types, nondisjunction and aneuploidy, transformation, transduction and conjugation, the PCR copy formula, the principle of gel electrophoresis and DNA sequencing.

• Predict the result of a density-label experiment from semiconservative replication
• Identify the roles of helicase, topoisomerase, DNA polymerase, primers and ligase
• Classify missense, nonsense and frameshift mutations from given codons and predict their effect
• Distinguish transformation, transduction and conjugation
• Interpret gel electrophoresis results, DNA fingerprints, PCR amplification and transformation plates

Practice material written by Zestly, based on the College Board AP Biology course framework (topics 6.2 DNA replication, 6.7 Mutations and 6.8 Biotechnology).