Biotechnology Terms Starting With A
Biotechnology Glossary: A
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Agrobacterium
/ ag-roh-bak-TEER-ee-um / · Latin ager, field; bacteria
Agrobacterium is a soil bacterium that naturally transfers a segment of its Ti plasmid DNA into plant cells, making it the most widely used vector for plant genetic engineering.
The transferred DNA integrates stably into the plant nuclear genome and is expressed using plant regulatory signals, enabling heritable transformation. Scientists replace the oncogenic T-DNA genes with genes of interest while retaining the border sequences required for transfer. Agrobacterium-mediated transformation has been used to create herbicide-resistant, insect-resistant, and nutritionally enhanced crop varieties worldwide.
Golden Rice, engineered to produce beta-carotene in the grain, was developed using Agrobacterium-mediated transformation of rice.
Agrobacterium is the only known bacterium that naturally transfers DNA into a eukaryotic nucleus. The mechanism it uses, threading single-stranded T-DNA through a type IV secretion system, shares structural similarities with the machinery some bacterial pathogens use to inject proteins into human cells.
Differences Between Plant and Animal Cells →Plant genetic engineering always uses machines to force DNA into cells. Agrobacterium delivers DNA biologically because it evolved that ability over millions of years of co-evolution with wounded plant tissue.
Genetic Engineering Pros and Cons →Agrobacterium tumefaciens (now reclassified as Rhizobium radiobacter) causes crown gall disease by transferring T-DNA into wounded plant tissue, triggering uncontrolled cell proliferation. In laboratory transformation experiments, researchers replace the tumor-causing genes with a gene of interest, and the resulting galls are replaced by regenerated, stably transformed shoots.
Artificial Selection
/ ar-tih-FISH-ul seh-LEK-shun / · Latin artificialis, made by art; selectio, choice
Artificial selection is the intentional breeding of organisms with desired traits by humans, accelerating trait frequency changes that would otherwise occur slowly through natural selection.
Artificial selection has shaped domesticated crops, livestock, and companion animals over thousands of years, producing organisms often dramatically different from their wild ancestors. Domestic dogs (Canis lupus familiaris) were selectively bred from wolves over at least 15,000 years, yielding breeds that differ in body mass by more than 40-fold. Modern genomic tools enable marker-assisted selection, letting breeders choose molecular variants linked to desired traits without waiting for full trait expression.
This approach has cut the time needed to fix favorable alleles in commercial wheat and maize breeding programs by several generations.
Teosinte, the wild ancestor of modern maize (Zea mays), produces ears less than 3 centimeters long with only about a dozen kernels. Fewer than ten genes with large effects account for most of the dramatic morphological difference between teosinte and the modern corn cob, illustrating how rapidly selection can reshape a plant.
Artificial selection creates brand-new traits from nothing. It increases or recombines traits already present in a population through standing genetic variation and occasional mutation, and cannot produce a trait for which no genetic basis exists in the breeding population.
Broccoli, cabbage, kale, and cauliflower were all bred from wild mustard (Brassica oleracea) by selecting different plant parts over roughly 2,000 years of cultivation. Human selection emphasized the flower head in broccoli, the terminal bud in cabbage, the leaves in kale, and the curd in cauliflower, producing four visually distinct vegetables from a single ancestral species.
Automated Sequencing
/ AW-toh-may-ted SEE-kwen-sing / · Latin automatus; sequi, to follow
Automated sequencing is an instrument-based approach to reading the order of nucleotides in a DNA molecule, replacing manual gel-based methods and enabling rapid, large-scale genome analysis at dramatically reduced cost.
First-generation automation applied fluorescent dye-labeled dideoxy terminators and capillary electrophoresis to Sanger sequencing, accelerating the Human Genome Project completed in 2003. Next-generation sequencing platforms advanced the field further by sequencing millions of DNA fragments simultaneously, reducing the cost of sequencing a human genome from roughly 3 billion dollars to under 1,000 dollars. Third-generation platforms, such as those developed by Pacific Biosciences and Oxford Nanopore Technologies, sequence single DNA molecules in real time and can directly detect chemical modifications such as methylation without additional sample preparation.
Oxford Nanopore's MinION sequencer weighs about 90 grams and plugs into a laptop's USB port, yet it can sequence an entire bacterial genome in a single run. Researchers used MinION devices in the field during the 2014 to 2016 Ebola outbreak in West Africa to identify viral strains within hours rather than waiting days for results from centralized laboratories.
Automated sequencing means a machine understands the biology by itself. Instruments produce raw signal data that requires substantial computational processing and expert biological interpretation before meaningful conclusions can be drawn.
The Human Genome Project relied on thousands of automated capillary electrophoresis sequencers running Sanger chemistry in parallel. Each instrument read fluorescently labeled DNA fragments and assigned base identities from the color of light emitted as fragments passed a laser detector, generating roughly 1,000 base pairs of readable sequence per capillary run.