Sequencing and transcriptomics

Daniel Fürth
Assistant professor
SciLifeLab/Uppsala University


📚🙇🏽‍♀️🙇🏻‍♂️📖 Learning goals

Course Syllabus: 🔗3MG022

Knowledge and understanding

“Explain current techniques for research, diagnostics and treatment of genetic diseases including cancer”

Competence and skills

“independently analyse, process and formulate relevant scientific questions…”

Judgement and approach

“…ability to critically evaluate and appraise scientific research…”

📚🙇🏽‍♀️🙇🏻‍♂️📖 Learning goals

Topics covered today:

  • 📜 History: from Sanger sequencing to single-cell methods
  • 🔎 Transcriptomic analysis
  • 🧬 Different types of RNAs and their functions

📜 Sanger sequencing ➡️ single-cell methods

Separation chemistry

Electrophoretic machine as designed by Tiselius

Separation chemistry

Polyacrylamide gel electrophoresis (PAGE)

  • Length
  • Charge
  • Confirmation

Molecules can be run in their “native state
preserving higher-order structure.

Or a chemical denaturant can be added to
remove structure (urea for 🧬).

Native vs non-native PAGE.

Pore size controled by % of acrylamide.

📏 Resolution:
100-1000 nt down to single-nucleotide.

Fredrick Sanger

  • One of the few who received two Noble Prizes.
    • 💉1958
      • “structure of proteins, especially that of insulin”

    • 🧬1980
      • “determination of base sequences in nucleic acids”

🇬🇧 Medical Research Council
Laboratory of Molecular Biology

Left MRC Laboratory of Molecular Biology, 1962. Right Left to right: Hugh Huxley, 🏅John Kendrew (’62), 🏅Max Perutz (’62), 🏅Francis Crick (’62), 🏅Fred Sanger (’58,’80) and
🏅Sydney Brenner (2002).

🛠🧰 Restriction enzymes 🧬

🇺🇸 Restriction and modification enzymes 🇨🇭

🏅Noble Prize: 🇺🇸 Hamilton O. Smith, 🇺🇸 Daniel Nathans, and 🇨🇭 Werner Arber.

Structure of a Ribonucleic Acid

Structure of a Ribonucleic Acid

RNase A (Bovine pancreas ribonuclease):

  • Only active on RNA.
  • Very sturdy, survives boiling etc 🔥.
  • Cleaves 3’-end of unpaired C and U residues (pyrimidine).

RNase T1 (Taka-Diastase ribonuclease T1):

  • Single-stranded (ssDNA or RNA) specific exonuclease
  • Catalyzes the removal of nucleotides from linear single-stranded DNA or RNA in the 3’ to 5’ direction

Nuclease Protection Assay (NPA)

A proto sequencing method.

Two-dimension partition sequencing

A proto sequencing method.

  • First seperate on isoelectric point (pI)
    • pH @ molecule has no net electric charge.
  • Then seperate on molecular weight.

Two-dimension partition sequencing

Two-dimension partition sequencing

dNTP incorporation has base specificity

The birth of the “-”-approach of Sanger.

First sequence of a single gene

  • Bacteriophage MS2
  • Circular ssDNA genome.

Sanger’s Plus/Minus sequencing

Sanger’s Plus/Minus sequencing

Dideoxynucleotides (ddNTP) are incorporated

Polymerases can incorporate ddNTPs.

Leading to a single base extension followed by termination

No 3’hydroxyl group (3’OH).

🏆 Chain-termination method 🏅

“Sanger sequencing”

Second Noble Prize

Maxam & Gilbert sequencing

  • Radioactive 5’labeling

  • Chemical cleavage

  • PAGE

The birth of biotech

California. Genentech and recombinant technologies were already creating value. Flow cytometer and Beckman Coulter commercial machines.

⛰ Cal. Tech. 👥 Leroy Hood and Mike Hunkapiller 🏢 Applied Bioscience Inc. (ABI)

Sanger sequencing

Fluorescently labeled nucleotides.

Sanger sequencing

Base calling: assigning specific nucleotide bases to raw signals generated during sequencing.

Human Genome Project

Next-generation sequencing

All about how to massively multiplex sequencing.

  • Pyrosequencing

  • Sequencing by ligation

  • Reversible dye-terminators

Solid-phase substrate

  • Bridge amplification

  • Emulsion PCR

  • DNA nanoballs

Primer extension

  • Sequencing by synthesis

  • Sequencing by ligation


Polony sequencing

Solexa/Illumina sequencing

  • Solid support: PCR bridge amplification
  • Primer extension: Reversible dye-terminators (patent 444 about to expire!)

Solexa/Illumina sequencing

Democratization of sequencing

RNA sequencing

  • Is actual DNA sequencing.

  • But the RNA is converted to cDNA by reverse transcriptase.

RNA sequencing

Single-cell RNA sequencing

🔎 Transcriptomic analysis

Primary, secondary, tertiary

Gene body and why to sequence

  • Alternative splicing

  • Intron retention, pre-mRNA

  • Alterative polyadenylation (3’UTR exon)


  • Allele-specific expression

🧬 Different types of RNAs and their functions

🧬 Different types of RNAs and their functions

🧬 Different types of RNAs and their functions