Gene Cloning
Class 12 · Biotechnology
5 ideas in Class 12 Biotechnology, explained in plain words, with games and quizzes to practise.
Getting the Gene Ready
Part of: Finding and Freeing the Gene
Cloning starts before any cutting: first pick the right gene using protein clues or a matching probe, then free clean DNA from cells in four moves, namely open the cells, guard the DNA from chewing enzymes, separate DNA from the rest, and check its purity and amount.
Why it matters. Skipping these moves poisons everything later: dirty or broken DNA cuts badly and copies poorly. Knowing the order helps you debug a failed extraction step by step.
Key words
- candidate gene
- : The chosen gene picked for cloning and study.
- probe
- : A labelled DNA piece that finds its matching sequence.
- nucleic acid isolation
- : Freeing clean DNA or RNA from cells.
- purity check
- : Tests that show how clean the freed DNA is.
- degrading enzyme
- : A protein that chews up unguarded nucleic acids.
Try it in two minutes
- Name the two jobs: choose the gene, then free clean DNA.
- Walk the four freeing moves in order: open, guard, separate, check.
- Ask what each move prevents: spill without opening, chewing without guarding, mixing without separating, blindness without checking.
Try at home. Write the four freeing moves on cards and shuffle them back into order.
Tool Enzymes of rDNA
Part of: Cutting, Pasting and Delivering
DNA surgery needs specialist proteins. Trimmers chew from the ends, inside-cutters open at defined sequences with the middle type doing lab duty, joiners seal breaks, builders copy strands, phosphate removers stop self-closing, and RNA readers write DNA copies from RNA.
Why it matters. Using the wrong enzyme ruins the plan: a trimmer cannot open a ring neatly and a joiner cannot cut. Matching job to enzyme is the core lab skill of this chapter.
Key words
- exonuclease
- : An enzyme that trims units from DNA ends.
- restriction enzyme
- : An enzyme that cuts DNA at a defined sequence.
- ligase
- : An enzyme that seals breaks between DNA pieces.
- reverse transcriptase
- : An enzyme that writes DNA using an RNA template.
- alkaline phosphatase
- : An enzyme that removes end phosphates from DNA.
Try it in two minutes
- Sort enzymes into cut, join, build and finish piles.
- Ask which cutter opens inside the strand and which only trims ends.
- Ask which tool seals breaks and which removes end phosphates.
Try at home. Make a four-pile chart of cut, join, build and finish enzymes.
Moving DNA into Hosts
Part of: Cutting, Pasting and Delivering
Finished carrier DNA must enter host cells, and several routes exist. Salt treatment makes bacterial walls leaky, fatty bubbles ferry DNA inside, electric pulses punch brief holes, fine needles place DNA directly, and particle devices dust DNA-coated specks onto cells.
Why it matters. No single route fits all hosts, so choosing by cell type saves failed attempts. Knowing how each route breaches the wall helps you pick one a given cell can survive.
Key words
- competent cell
- : A cell treated so it readily takes in outside DNA.
- electroporation
- : A brief electric pulse that opens pores for DNA entry.
- microinjection
- : Placing DNA with a fine needle straight into a cell.
- particle bombardment
- : Dusting DNA-coated specks onto target cells.
- lipofection
- : Ferrying DNA inside fatty bubbles that merge with cells.
Try it in two minutes
- Group routes into chemical helpers and physical forces.
- Ask how each route crosses the wall: leak, ferry, pulse, needle or dust.
- Ask which route suits fragile animal cells versus tough plant cells.
Try at home. List each delivery route with the cell type it suits best.
Finding the Right Clones
Part of: Selecting, Detecting and Storing
After delivery, most cells lack the wanted carrier, so growers filter them out. Direct growth on a selective chemical keeps carriers, breaking a second marker proves pasting, colour tests flag inserts, and blot tests confirm the exact DNA, RNA or protein using matching probes.
Why it matters. Without filtering, the wanted cells hide among millions of empties. These tricks turn a blind hunt into a short checklist of plates and bands.
Key words
- direct selection
- : Keeping only carrier-holding cells on selective plates.
- insertional inactivation
- : Breaking a marker gene by pasting inside it.
- Southern blot
- : A probe test that detects a defined DNA stretch.
- Northern blot
- : A probe test that detects a defined RNA.
- Western blot
- : A probe test that detects a defined protein.
Try it in two minutes
- Order the hunt: keep carriers, prove pasting, confirm the molecule.
- Ask which plate keeps carriers and which second plate proves the paste.
- Ask which blot letter fits DNA, RNA and protein each.
Try at home. Write which blot letter detects DNA, RNA and protein from memory.
Copying and Banking DNA
Part of: Selecting, Detecting and Storing
Tiny DNA amounts can be multiplied with heat cycles: split the strands, seat short starters, then extend new copies, repeating to explode numbers. Gene banks store two kinds of sets: whole-genome collections with every stretch, and message-based collections with only active genes.
Why it matters. Amplification rescues trace samples and banks save hunting time later. Knowing cycle logic and bank types tells you when to multiply and where to search.
Key words
- denaturation
- : Heat-splitting of double DNA into single strands.
- annealing
- : Seating of short starters onto matching spots.
- extension
- : Building of new strands from seated starters.
- genomic library
- : A stored set covering the whole genome.
- cDNA library
- : A stored set covering only active genes.
Try it in two minutes
- Mime the three cycle moves: split, seat, extend.
- Ask why repeats explode counts instead of adding.
- Ask which bank holds silent stretches and which holds only active genes.
Try at home. Name the three cycle moves and the two bank types from memory.
What your child will practise
- Copying and Banking DNA: Jungle Quick Fire (Quick Fire)
- Finding the Right Clones: Candy Puzzle (Clue Puzzle)
- Getting the Gene Ready: Desert Quick Fire (Quick Fire)
- Moving DNA into Hosts: Space Puzzle (Clue Puzzle)
- Tool Enzymes of rDNA: Ocean Quick Fire (Quick Fire)
- Quiz: Copying and Banking DNA (8 questions)
- Quiz: Finding the Right Clones (8 questions)
- Quiz: Getting the Gene Ready (8 questions)
- Quiz: Moving DNA into Hosts (8 questions)