Sequencing Techniques & Applications in Biomedical Science

Vocabulary flashcards covering key terms from the lecture on DNA sequencing technologies, their history, principles, and applications.

Sanger sequencing

First-generation DNA sequencing method that uses chain-terminating dideoxy nucleotides to read DNA bases one by one.

Chain-terminating dideoxy nucleotide (ddNTP)

A modified nucleotide lacking a 3′-OH group; when incorporated, it stops DNA strand extension.

Primer extension

Process in which DNA polymerase adds nucleotides to a short primer in the 5′→3′ direction to synthesize new DNA.

DNA polymerase

Enzyme that catalyzes DNA synthesis by adding nucleotides to a growing strand during sequencing or replication.

Polyacrylamide gel electrophoresis (PAGE)

High-resolution gel method used in early Sanger sequencing to separate DNA fragments by size.

Fluorescent chain terminator

ddNTP tagged with a fluorescent dye, allowing automated detection of terminated fragments.

Capillary sequencer (e.g., ABI 3730)

Automated instrument that separates fluorescently labeled fragments in capillaries, greatly increasing sequencing throughput.

Human Genome Project (HGP)

International effort that produced the first draft human genome in 2001; cost ≈ $2.7 billion and used Sanger technology.

Next Generation Sequencing (NGS)

High-throughput sequencing platforms that parallelize millions of reads, dramatically lowering cost and time.

Read length

Number of consecutive bases determined in a single sequencing read (≈ 1 kb for Sanger, 50–300 bp for many NGS runs).

RNA-seq

NGS application that sequences complementary DNA from RNA to analyze transcriptomes quantitatively.

ChIP-seq

Technique combining chromatin immunoprecipitation with sequencing to map protein–DNA interactions genome-wide.

Bioinformatics

Computational discipline that stores, processes, and analyzes large biological data sets such as sequencing reads.

'Omics

Collective term for large-scale biological data fields (genomics, transcriptomics, proteomics, etc.).

Genome

Complete set of an organism’s DNA; human genome contains ~3.2 billion base pairs.

Base pair (bp)

Pair of complementary nucleotides (A–T or G–C) forming the basic unit of double-stranded DNA length measurement.

ddNTP labeling

Attachment of radioactive or fluorescent tags to ddNTPs to visualize terminated fragments during sequencing.

Laser detection

Optical system in automated sequencers that excites fluorescent dyes and records emitted signals for base calling.

Q30 quality score

Sequencing accuracy metric indicating 1 error per 1000 bases (99.9 % accuracy).

3′ hydroxyl (3′-OH) group

Functional group on deoxyribose required for nucleotide chain elongation; absent in ddNTPs.

Chain termination

Halting of DNA synthesis when a ddNTP is incorporated, producing fragments of defined lengths.

5′→3′ DNA synthesis

Directional property of DNA polymerase adding nucleotides to the 3′ end of the growing strand.

Polymerase Chain Reaction (PCR)

Technique amplifying specific DNA regions; developed after initial Sanger studies and now routine in sequencing workflows.

Gel autoradiograph

X-ray film image showing radiolabeled DNA fragments separated on a gel, used to manually read early sequences.

Fluorescent chemistry

Use of dye-labeled nucleotides enabling non-radioactive, automated sequencing detection.

Data storage & computing power

Technological advances that allow handling of massive sequencing datasets generated by NGS platforms.

Single-sample limitation

Drawback of traditional Sanger sequencing that processes one DNA template per reaction, restricting throughput.

Sequencing applications

Biomedical uses such as disease gene discovery, personalized medicine, diagnostics, evolutionary studies, and microbiome profiling.