Biotechnology and Genomics

This is Unit Seven of Biology, Part One: the toolkit and what it is used for. Genomics is not another word for genetics. Genetics studies individual genes and how they are inherited; genomics studies a genome as a system — its whole gene set, its sequence, its organisation and its interactions. Then the tools, and each one does something narrower than its reputation suggests. Gel electrophoresis separates fragments by size and reveals nothing about their sequence. The polymerase chain reaction copies only what sits between its two primers, not a genome indiscriminately. And reverse transcriptase P C R is two reactions, with the first one finished before the second begins. The middle of the part is cutting and joining. A restriction enzyme cuts at one specific sequence and leaves overhangs, and two pieces cut by the same enzyme carry complementary overhangs — which is the entire reason recombinant D N A works. Then cloning, where the standing misconception is that a clone is an identical copy. It is not: mitochondrial D N A comes from the recipient egg, and environment and epigenetic marks differ too. The part closes on applications — three of them touching human health, each stating its own limit. By the end you will be able to do five things. One: say what genomics studies. Two: say what each technique reveals. Three: say why cut ends join. Four: say why a clone is not identical. Five: read a genetic test result.

Five entries. One defines the field and four are laboratory techniques. Every one of the four carries a warning narrowing what it actually does, and reading those warnings together is the point of the topic.

The whole genome.

Bio 1521 Genomics Defined

Genomics studies an organism's entire genome — its complete gene set, sequence, organisation and interactions — so comparing every gene on every chromosome, rather than one gene alone, is a genomic-scale study. It is not a synonym for genetics: genetics studies individual genes and inheritance, genomics studies the genome as a system.

Sorting by size.

Bio 1523 Gel Electrophoresis

Gel electrophoresis separates D N A or R N A fragments by size, using an electric field to pull the negatively charged fragments through a porous gel — smaller ones travel farther, forming a ladder of bands. It separates by size alone and does not itself reveal any fragment's sequence.

Copying one region.

Bio 1525 PCR: Amplifying a Target DNA Sequence

The polymerase chain reaction amplifies one specific D N A region into many copies, using primers flanking the target and a heat-stable polymerase, with repeated heating and cooling copying the stretch exponentially. It amplifies only the sequence its primers flank; it does not copy a whole genome indiscriminately.

Starting from R N A.

Bio 1527 RT-PCR: Amplifying from an RNA Template

Reverse transcriptase P C R first converts an R N A template into complementary D N A, then amplifies that D N A with ordinary P C R. The first step is reverse transcription, a distinct reaction from P C R itself — the amplification only begins once complementary D N A already exists.

Finding a sequence.

Bio 1529 Southern and Northern Blotting

Blotting transfers separated fragments onto a membrane and probes them with a labelled sequence, which binds only the complementary fragment and reveals whether that sequence is present. Southern blotting detects D N A and Northern detects R N A — while a third technique, Western blotting, probes proteins instead.

Four entries and the mechanical core of the unit. An enzyme that cuts at one sequence, a carrier that holds what you cut out, the procedure that joins them, and what the result produces once a cell reads it.

The cut.

Bio 1531 Restriction Endonucleases and Sticky Ends

A restriction endonuclease recognises a specific D N A sequence and cuts both strands there, often leaving short single-stranded overhangs called sticky ends — two fragments, each with a complementary overhang. Each enzyme cuts only at its own recognition sequence, and different enzymes cannot substitute for one another.

The carrier.

Bio 1533 The Plasmid Vector

A plasmid is a small circular D N A molecule replicating independently of a bacterial chromosome, able to carry inserted D N A as a vector — its multiple cloning site holds several restriction sites, offering a choice of insertion point. Because it replicates independently, inserting D N A leaves the bacterium's own chromosomal genes unaltered.

Putting them together.

Bio 1535 Constructing a Recombinant Plasmid

Treat both a foreign fragment and a plasmid with the same restriction enzyme. The plasmid opens from a circle into a linear molecule with two sticky ends, and the fragment carries complementary overhangs, so the two anneal. Annealing leaves gaps in the backbone, since base pairing does not join strands covalently, and ligase — the same enzyme sealing Okazaki fragments in replication — closes each gap. The result is a circular plasmid carrying the fragment as part of its sequence. Two pieces cut by different enzymes will not anneal.

Getting a protein.

Bio 1537 Recombinant Proteins

A recombinant protein is what a recombinant D N A molecule produces once its host cell transcribes and translates the inserted gene — a bacterium carrying a plasmid with a human gene makes the human protein alongside its own. Inserting a gene supplies only the sequence; expression still needs the host's own machinery.

Three entries. The word covers two quite different things — one about cells and one about whole organisms — and the third entry corrects the assumption almost everyone brings to the second.

At the cell level.

Bio 1539 Cellular Cloning

Cellular cloning is the natural production of genetically identical cell populations, as when a unicellular organism replicates asexually — a bacterium dividing by binary fission gives two daughter cells with the same sequence. It describes single cells reproducing identical copies; reproducing a whole multicellular organism is a separate process.

At the organism level.

Bio 1541 Reproductive Cloning and Somatic Cell Nuclear Transfer

Reproductive cloning produces a genetically matched organism by somatic cell nuclear transfer — moving a donor's diploid nucleus into an enucleated egg, as with Dolly the sheep in nineteen ninety-six. Nuclear transfer supplies the donor's nuclear D N A; the egg's own cytoplasm still shapes early development.

The standing error.

Bio 1543 "A Clone Is a Perfect Identical Copy"

A reproductive clone is not a perfect identical copy of its donor, because mitochondrial D N A, environment and epigenetic marks all still differ — the clone's mitochondrial D N A comes from the recipient egg rather than the donor, so its full genome never matches. Matching nuclear D N A is not matching every heritable influence.

Two entries. One defines deliberate genome alteration and distinguishes two terms people use interchangeably. The other turns the technique into a research method, and its warning is about which direction the reasoning runs.

Deliberate alteration.

Bio 1545 Genetic Engineering and Transgenic Organisms

Genetic engineering alters an organism's genotype using recombinant D N A technology, and an organism receiving D N A from a different species this way is transgenic — as a crop carrying a bacterial gene would be. Transgenic is the narrower term: it requires D N A from another species, where the broader label covers any deliberate genome alteration.

Finding out what a gene does.

Bio 1547 Gene Targeting and Reverse Genetics

Gene targeting uses recombinant vectors to disable or mutate a specific gene, letting researchers infer its function from what changes — delete one gene, observe the lost function. This is reverse genetics: it starts from sequence and works toward a phenotype, where classical genetics starts from a phenotype and works back.

Five entries, and each one states a limit on itself. Two are agricultural and three touch human health — and those three are the reason this lecture carries the course's medical disclaimer throughout.

Making a human protein.

Bio 1549 Recombinant Protein Production in Medicine

Recombinant D N A technology lets bacterial or animal hosts mass-produce a human protein by expressing a cloned human gene — a bacterial host carrying the cloned human insulin gene produces human insulin directly, where earlier preparations were purified from animal pancreases. Recombinant insulin is human insulin made in a bacterial host, not an artificial or animal-derived substitute.

Into a plant.

Bio 1551 Agrobacterium-Mediated Plant Transformation

A soil bacterium naturally transfers D N A from its own plasmid into a plant's genome, and researchers repurpose that by removing the plasmid's tumour-causing genes and replacing them with a chosen fragment, which the bacterium then delivers. The unmodified plasmid causes tumours — those genes are removed specifically for transformation.

A crystal protein.

Bio 1553 Bt Toxin as an Organic Insecticide

A soil bacterium produces a protein crystal toxic to specific insects when ingested, and cloning its gene into a plant makes the plant insecticidal — insects that ingest it stop feeding within hours. The toxin has to be ingested and activated in the insect gut; it is not a contact poison, and is nontoxic to mammals.

Looking for a variant.

Bio 1555 Genetic Testing

Genetic testing analyses an individual's D N A sequence to detect a specific variant already known to be associated with a disease — which is a different thing from evaluating that person's health directly. A test detects only the variants it targets, so a negative result does not rule the disease out.

Adding a working copy.

Bio 1557 Gene Therapy

Gene therapy introduces a functional gene copy into patient cells by a viral vector, to compensate for a disease-causing mutated gene — the vector infects target cells and delivers the working gene alongside the patient's own mutated copy. Basic gene therapy adds a functional copy; it does not remove or repair the defect.

Five things to carry out of Part One. Genomics studies a genome as a system — its whole gene set, sequence, organisation and interactions — where genetics studies individual genes and their inheritance. The two are not interchangeable words for one field. Each technique does one narrow thing. Electrophoresis separates fragments by size and says nothing about sequence. The polymerase chain reaction copies only what lies between its two primers. Reverse transcriptase P C R adds a prior reaction that makes D N A from R N A first. Blotting probes a membrane for one sequence — Southern for D N A, Northern for R N A, Western for protein. Two pieces of D N A cut by the same restriction enzyme join because that enzyme leaves complementary single-stranded overhangs on both. Annealing alone leaves gaps in the backbone, so ligase seals them. Pieces cut by different enzymes carry mismatched overhangs and will not anneal. A clone is not an identical copy. Nuclear transfer supplies the donor's nuclear D N A only — mitochondrial D N A comes from the recipient egg, and environment and epigenetic marks differ as well. Matching nuclear D N A is not matching every heritable influence. And a genetic test detects only the specific variants it is built to target, so a negative result does not rule the disease out. Gene therapy, likewise, adds a working gene copy alongside the mutated one rather than removing or repairing it. Part Two turns to mapping and sequencing a genome, and to what is read from it afterward.