Homeworks

Subsections of Homeworks

Week 1 HW: Principles and Practices

cover image cover image

Process of Researching the project:

I looked at some iGem projects to gain inspiration and a sense of the types of topics that people have addressed. https://video.igem.org/c/2025_presentations/videos

First, describe a biological engineering application or tool you want to develop and why.

Vitiligo is an autoimmune condition characterized by the selective loss of melanocytes, leading to depigmented skin lesions. A growing body of evidence suggests that elevated oxidative stress in melanocytes precedes and exacerbates immune-mediated destruction by increasing cellular damage and inflammatory signaling.

My project proposes an oxidative-stress–responsive genetic circuit in melanocytes that activates cytoprotective pathways only under pathological redox conditions and automatically deactivates once oxidative stress resolves. By enhancing stress resilience rather than inducing pigmentation, this approach aims to reduce melanocyte vulnerability while minimizing unintended cosmetic or immune effects.

Goals:

  1. Prevent Harm: Prevent the technology from causing biological, social, or psychological harm. • A1. Prevent biological harm from uncontrolled gene expression, persistence, or immune disruption. • A2 Prevent social harm, including stigmatization, cosmetic misuse, or reinforcement of colorism. • A3 Prevent misuse or repurposing beyond therapeutic, supportive contexts.

  2. Promote Safe and Constructive Innovation: Enable beneficial research and translation without unnecessary restriction.

    • B1. Encourage disease-aligned, upstream interventions (stress resilience vs cosmetic alteration). • B2. Avoid chilling effects on legitimate academic research. • B3. Support iterative learning and transparency around failures.

  3. Respect Autonomy, Equity, and Trust • C1. Incorporate patient perspectives into design and deployment decisions. • C2. Avoid one-size-fits-all assumptions about desirability of treatment. • C3. Ensure accessibility and avoid disproportionate burdens on marginalized groups.

Next, describe at least three different potential governance “actions” by considering the four aspects below (Purpose, Design, Assumptions, Risks of Failure & “Success”).

Governance Action 1: Mandatory Design-Layer Safeguards for Stress-Responsive Therapeutics

  • Purpose: Require that stress-responsive therapeutic circuits incorporate reversibility, thresholding, and containment as baseline design criteria.
  • Design: Circuits must be inducible and auto-deactivating.
  • Assumptions: design constraints meaningfully reduce harm, researchers can implement safeguards without prohibitive cost, reviewers can competently assess circuit-level safety claims.
  • Failure risks: Smaller labs may be excluded due to resource burden.

    Governance Action 2: Patient-Guided Scope Limitation via Advisory Committees

  • Purpose: Require early-stage patient advisory input for disease-facing synthetic biology projects, particularly for visible or identity-linked conditions.
  • Design: Structured advisory committees (e.g., Vitiligo Patient Advisory Committee).
  • Assumptions: Diversity of patient views can be captured.
  • Risks of Failure & “Success”: Overrepresentation of certain demographics, Projects may narrow scope so much that some beneficial uses are delayed.

    Governance Action 3: Transparency & Post-Research Monitoring Norms

  • Purpose:Establish norms for transparent disclosure of assumptions, limitations, and misuse risks, even for preclinical tools
  • Design: Public documentation of design assumptions and failure modes, Scenario analysis of misuse or unintended deployment.
  • Assumptions:Transparency deters misuse.
  • Risks of Failure & “Success”: Sensitive details could be misused.

    3. Scoring Governance Actions Against Policy Goals

    (1 = best, 3 = weakest, n/a = not applicable)

    Governance Action / Policy GoalOption 1
    Design Safeguards
    Option 2
    Patient Governance
    Option 3
    Transparency
    A. Prevent Biological Harm122
    • A1 Biological safety132
    • A2 Social harm212
    • A3 Misuse prevention221
    B. Promote Constructive Use211
    • B1 Disease alignment112
    • B2 Not impede research211
    • B3 Learning from failure221
    C. Autonomy & Trust312
    • C1 Patient voicen/a12
    • C2 Respect diversity212
    • C3 Equity221–2

    Prioritize a combined strategy centered on Option 1 (Design Safeguards) and Option 2 (Patient Governance), with Option 3 (Transparency) as a supporting layer. Option 1 scored strongest on preventing biological harm (A1) and performed well on misuse prevention. Because the MelanoGuard system directly manipulates cellular stress-response pathways, technical harm prevention must occur at the level of the biological system itself, not solely through external oversight. Option 2 scored best on social harm prevention (A2), autonomy and trust (C), and constructive use (B). Vitiligo is a visible, identity-linked condition, so ethical failure is more likely to occur at the social level than the molecular level. Option 3 scored highest for misuse detection (A3) and learning from failure (B3), but weaker on direct harm prevention and trust building.

    Lecture 2 Slides 1 Q/A

    Nature’s machinery for copying DNA is called polymerase.

  • What is the error rate of polymerase?
    1:10⁶ (error:base-pairs)
  • How does this compare to the length of the human genome. How does biology deal with that discrepancy?
    Human genomee is ~3.2 X 10⁹ base pairs. That would be 3200 errors. Biology has error correction and has a proof reading step and a post-replication mismatch repair.
  • How many different ways are there to code (DNA nucleotide code) for an average human protein? In practice what are some of the reasons that all of these different codes don’t work to code for the protein of interest? Average human protein is ~1036 BP. Each codon is 3 BP, so 1036/3 = 345 amino acids. On an average there are 3 synonymous codons per amino acid. so ~3^345 different ways. There are physical and structural consntraints.

    Lecture 2 Slides 2 Q/A

    1. What is the most commonly used method for oligo synthesis today?
      all commercial oligos today are made using phosphoramidite chemistry.
    2. Why is it difficult to make oligos longer than ~200 nt by direct synthesis?
      Error accumulation per synthesis cycle and errors compound exponentially.
    3. Why can’t you make a 2000 bp gene via direct oligo synthesis?
      Direct synthesis scales exponentially poorly, not linearly and errors would be everywhere

    Lecture 2 Slides 3 Q/A

    What are the 10 essential amino acids in all animals and how does this affect your view of the “Lysine Contingency”? 1. Histidine 2. Isoleucine 3. Leucine 4. Lysine 5. Methionine 6. Phenylalanine 7. Threonine 8. Tryptophan 9. Valine 10. Arginine

    So, #4 shows that all animals have in Lysine. Microbes and plants can synthesize all 20 canonical amino acids. This is why lysine biosynthesis pathways exist in bacteria but not animals. In animals (including humans) Lysine is always externally supplied, Cells already operate under lysine dependency. Therefore, Lysine contingency does NOT inherently restrict survival and is not a meaningful containment mechanism in animal hosts. Lysine contingency can function as containment in microbes, but only if: The environment lacks lysine, No cross-feeding occurs, No bypass pathways evolve. Lysine contingency should never be used alone and should be combined with the following so that animals can’t supply it, Microbes can’t evolve it easily and Environment doesn’t contain it:

    •	Genetic code recoding
    •	Non-standard amino acid dependence
    •	Codon reassignment
    •	Virus resistance
    •	Metabolic isolation
    

    Knowing that lysine is one of the 10 essential amino acids in all animals makes it clear that lysine contingency alone is not a robust biocontainment strategy; it only becomes meaningful when combined with genetic code engineering or dependence on non-standard amino acids. Because lysine is essential to all animals and ubiquitously available through diet and environment, “lysine contingency” by itself is biologically weak and only functions as a safety mechanism when embedded in a larger framework of genetic code recoding and metabolic isolation.

    [Given slides #2 & 4 (AA:NA and NA:NA codes)] What code would you suggest for AA:AA interactions?

    Collapse AA pairs into a small set of symbols:

    •	HΦ: hydrophobic packing (Leu/Ile/Val/Phe…)
    •	HB: hydrogen-bond pairing (polar donors/acceptors)
    •	SB: salt bridge (Asp/Glu ↔ Lys/Arg/His; pH-dependent)
    •	π: aromatic stacking / cation–π (Phe/Tyr/Trp with Lys/Arg)
    •	SS: disulfide bond (Cys–Cys)
    •	M: metal coordination (His/Cys/Asp/Glu and specific metals)
    •	G/P: geometry breakers (Gly flexibility, Pro rigidity)
    •	X: steric/charge clash (strongly unfavorable)
    

    Now an AA:AA “codeword” is something like:

    •	(Asp, Lys) → SB
    •	(Cys, Cys) → SS
    •	(Phe, Tyr) → π
    •	(Leu, Ile) → HΦ
    

    ChatGPT prompts:

    1. Tell me about NRF2–KEAP1 pathway and the role it plays in Vitiligo
    2. Are there any scientific issues with my explanation: “Vitiligo is is an autoimmune disease where oxidative stress in Melanocytes triggers immune system to attack them causing pigmentation. The idea I’m considering is developing a oxidative stress sensing mechanism that regulates a genetic circuit which turns on the protective mechanism in melanocytes until oxidative stress is active, and turns off the the protection when no oxidative stress is detected.”
    3. Create a narrative based on the slides (for all the slides from lecture 2)
    4. What’s Lysine Contingency
    5. If Lysine is already produced endogenously, why is used as a biocontainment strategy?
  • Week 2 HW: DNA Read, Write, and Edit

    Part 3: DNA Design Challenge

    Boltz 3D Structure Boltz 3D Structure

    3.1 Protein of interest:

    I’m interested in exploring JAK1 protein that is implicated in autoimmune diseases. I chose this by finding which are the priority protein targets for treatment of conditions like Vitiligo. Link to the protein from Uniprot: https://rest.uniprot.org/uniprotkb/P23458.fasta

    Protein Sequence:

    >sp|P23458|JAK1_HUMAN Tyrosine-protein kinase JAK1 OS=Homo sapiens OX=9606 GN=JAK1 PE=1 SV=2
    MQYLNIKEDCNAMAFCAKMRSSKKTEVNLEAPEPGVEVIFYLSDREPLRLGSGEYTAEEL
    CIRAAQACRISPLCHNLFALYDENTKLWYAPNRTITVDDKMSLRLHYRMRFYFTNWHGTN
    DNEQSVWRHSPKKQKNGYEKKKIPDATPLLDASSLEYLFAQGQYDLVKCLAPIRDPKTEQ
    DGHDIENECLGMAVLAISHYAMMKKMQLPELPKDISYKRYIPETLNKSIRQRNLLTRMRI
    NNVFKDFLKEFNNKTICDSSVSTHDLKVKYLATLETLTKHYGAEIFETSMLLISSENEMN
    WFHSNDGGNVLYYEVMVTGNLGIQWRHKPNVVSVEKEKNKLKRKKLENKHKKDEEKNKIR
    EEWNNFSYFPEITHIVIKESVVSINKQDNKKMELKLSSHEEALSFVSLVDGYFRLTADAH
    HYLCTDVAPPLIVHNIQNGCHGPICTEYAINKLRQEGSEEGMYVLRWSCTDFDNILMTVT
    CFEKSEQVQGAQKQFKNFQIEVQKGRYSLHGSDRSFPSLGDLMSHLKKQILRTDNISFML
    KRCCQPKPREISNLLVATKKAQEWQPVYPMSQLSFDRILKKDLVQGEHLGRGTRTHIYSG
    TLMDYKDDEGTSEEKKIKVILKVLDPSHRDISLAFFEAASMMRQVSHKHIVYLYGVCVRD
    VENIMVEEFVEGGPLDLFMHRKSDVLTTPWKFKVAKQLASALSYLEDKDLVHGNVCTKNL
    LLAREGIDSECGPFIKLSDPGIPITVLSRQECIERIPWIAPECVEDSKNLSVAADKWSFG
    TTLWEICYNGEIPLKDKTLIEKERFYESRCRPVTPSCKELADLMTRCMNYDPNQRPFFRA
    IMRDINKLEEQNPDIVSEKKPATEVDPTHFEKRFLKRIRDLGEGHFGKVELCRYDPEGDN
    TGEQVAVKSLKPESGGNHIADLKKEIEILRNLYHENIVKYKGICTEDGGNGIKLIMEFLP
    SGSLKEYLPKNKNKINLKQQLKYAVQICKGMDYLGSRQYVHRDLAARNVLVESEHQVKIG
    DFGLTKAIETDKEYYTVKDDRDSPVFWYAPECLMQSKFYIASDVWSFGVTLHELLTYCDS
    DSSPMALFLKMIGPTHGQMTVTRLVNTLKEGKRLPCPPNCPDEVYQLMRKCWEFQPSNRT
    SFQNLIEGFEALLK

    3.2. Reverse Translate: Protein (amino acid) sequence to DNA (nucleotide) sequence.

    Reverse Translate Reverse Translate

    DNA Sequence for homosapien using codon optimization tool in benchling:
    ATGCAGTACCTGAACATCAAGGAGGACTGCAACGCCATGGCCTTCTGCGCCAAGATGAGAAGCAGCAAGAAGACCGAGGTGAACCTGGAGGCCCCCGAGCCCGGCGTGGAGGTGATCTTCTACCTGAGCGACAGAGAGCCCCTGAGGCTGGGCAGCGGCGAGTACACCGCCGAGGAGCTGTGCATCAGAGCCGCCCAGGCCTGCAGGATCAGCCCCCTGTGCCACAACCTGTTCGCCCTGTACGACGAGAACACCAAGCTGTGGTACGCCCCCAACAGGACCATCACCGTGGACGACAAGATGAGCCTGAGGCTGCACTACAGGATGAGGTTCTACTTCACCAACTGGCACGGCACCAACGACAACGAGCAGAGCGTGTGGAGGCACAGCCCCAAGAAGCAGAAGAACGGCTACGAGAAGAAGAAGATCCCCGACGCCACCCCCCTGCTGGACGCCAGCAGCCTGGAGTACCTGTTCGCCCAGGGCCAGTACGACCTGGTGAAGTGCCTGGCCCCCATCAGGGACCCCAAGACCGAGCAGGACGGCCACGACATCGAGAACGAGTGCCTGGGCATGGCCGTGCTGGCCATCAGCCACTACGCCATGATGAAGAAGATGCAGCTGCCCGAGCTGCCCAAGGACATCAGCTACAAGAGGTACATCCCCGAGACCCTGAACAAGAGCATCAGGCAGAGGAACCTGCTGACCAGAATGAGGATCAACAACGTGTTCAAGGACTTCCTGAAGGAGTTCAACAACAAGACCATCTGCGACAGCAGCGTGAGCACCCACGACCTGAAGGTGAAGTACCTGGCCACCCTGGAGACCCTGACCAAGCACTACGGCGCCGAGATCTTCGAGACCAGCATGCTGCTGATCAGCAGCGAGAACGAGATGAACTGGTTCCACAGCAACGACGGCGGCAACGTGCTGTACTACGAGGTGATGGTGACCGGCAACCTGGGCATCCAGTGGAGGCACAAGCCCAACGTGGTGAGCGTGGAGAAGGAGAAGAACAAGCTGAAGAGGAAGAAGCTGGAGAACAAGCACAAGAAGGACGAGGAGAAGAACAAGATCAGGGAGGAGTGGAACAACTTCAGCTACTTCCCCGAGATCACCCACATCGTGATCAAGGAGAGCGTGGTGAGCATCAACAAGCAGGACAACAAGAAGATGGAGCTGAAGCTGAGCAGCCACGAGGAGGCCCTGAGCTTCGTGAGCCTGGTGGACGGCTACTTCAGGCTGACCGCCGACGCCCACCACTACCTGTGCACCGACGTGGCCCCCCCCCTGATCGTGCACAACATCCAGAACGGCTGCCACGGCCCCATCTGCACCGAGTACGCCATCAACAAGCTGAGACAGGAGGGCAGCGAGGAGGGCATGTACGTGCTGAGGTGGAGCTGCACCGACTTCGACAACATCCTGATGACCGTGACCTGCTTCGAGAAGAGCGAGCAGGTGCAGGGCGCCCAGAAGCAGTTCAAGAACTTCCAGATCGAGGTGCAGAAGGGCAGGTACAGCCTGCACGGCAGCGACAGGAGCTTCCCCAGCCTGGGCGACCTGATGAGCCACCTGAAGAAGCAGATCCTGAGGACCGACAACATCAGCTTCATGCTGAAGAGGTGCTGCCAGCCCAAGCCCAGAGAGATCAGCAACCTGCTGGTGGCCACCAAGAAGGCCCAGGAGTGGCAGCCCGTGTACCCCATGAGCCAGCTGAGCTTCGACAGGATCCTGAAGAAGGACCTGGTGCAGGGCGAGCACCTGGGCAGAGGCACCAGGACCCACATCTACAGCGGCACCCTGATGGACTACAAGGACGACGAGGGCACCAGCGAGGAGAAGAAGATCAAGGTGATCCTGAAGGTGCTGGACCCCAGCCACAGGGACATCAGCCTGGCCTTCTTCGAGGCCGCCAGCATGATGAGGCAGGTGAGCCACAAGCACATCGTGTACCTGTACGGCGTGTGCGTGAGGGACGTGGAGAACATCATGGTGGAGGAGTTCGTGGAGGGCGGCCCCCTGGACCTGTTCATGCACAGGAAGAGCGACGTGCTGACCACCCCCTGGAAGTTCAAGGTGGCCAAGCAGCTGGCCAGCGCCCTGAGCTACCTGGAGGACAAGGACCTGGTGCACGGCAACGTGTGCACCAAGAACCTGCTGCTGGCCAGGGAGGGCATCGACAGCGAGTGCGGCCCCTTCATCAAGCTGAGCGACCCCGGCATCCCCATCACCGTGCTGAGCAGGCAGGAGTGCATCGAGAGGATCCCCTGGATCGCCCCCGAGTGCGTGGAGGACAGCAAGAACCTGAGCGTGGCCGCCGACAAGTGGAGCTTCGGCACCACCCTGTGGGAGATCTGCTACAACGGCGAGATCCCCCTGAAGGACAAGACCCTGATCGAGAAGGAGAGGTTCTACGAGAGCAGATGCAGGCCCGTGACCCCCAGCTGCAAGGAGCTGGCCGACCTGATGACCAGGTGCATGAACTACGACCCCAACCAGAGGCCCTTCTTCAGAGCCATCATGAGGGACATCAACAAGCTGGAGGAGCAGAACCCCGACATCGTGAGCGAGAAGAAGCCCGCCACCGAGGTGGACCCCACCCACTTCGAGAAGAGGTTCCTGAAGAGGATCAGGGACCTGGGCGAGGGCCACTTCGGCAAGGTGGAGCTGTGCAGATACGACCCCGAGGGCGACAACACCGGCGAGCAGGTGGCCGTGAAGAGCCTGAAGCCCGAGAGCGGCGGCAACCACATCGCCGACCTGAAGAAGGAGATCGAGATCCTGAGGAACCTGTACCACGAGAACATCGTGAAGTACAAGGGCATCTGCACCGAGGACGGCGGCAACGGCATCAAGCTGATCATGGAGTTCCTGCCCAGCGGCAGCCTGAAGGAGTACCTGCCCAAGAACAAGAACAAGATCAACCTGAAGCAGCAGCTGAAGTACGCCGTGCAGATCTGCAAGGGCATGGACTACCTGGGCAGCAGGCAGTACGTGCACAGGGACCTGGCCGCCAGGAACGTGCTGGTGGAGAGCGAGCACCAGGTGAAGATCGGCGACTTCGGCCTGACCAAGGCCATCGAGACCGACAAGGAGTACTACACCGTGAAGGACGACAGGGACAGCCCCGTGTTCTGGTACGCCCCCGAGTGCCTGATGCAGAGCAAGTTCTACATCGCCAGCGACGTGTGGAGCTTCGGCGTGACCCTGCACGAGCTGCTGACCTACTGCGACAGCGACAGCAGCCCCATGGCCCTGTTCCTGAAGATGATCGGCCCCACCCACGGCCAGATGACCGTGACCAGACTGGTGAACACCCTGAAGGAGGGCAAGAGGCTGCCCTGCCCCCCCAACTGCCCCGACGAGGTGTACCAGCTGATGAGGAAGTGCTGGGAG

    3.4. You have a sequence! Now what? What technologies could be used to produce this protein from your DNA? Describe in your words the DNA sequence can be transcribed and translated into your protein. You may describe either cell-dependent or cell-free methods, or both.

    At first, Transcribe the DNA sequence to mRNA by inserting the DNA into living cells. The DNA template strand is read 3’ to 5’ and mRNA is synthesized 5’ to 3’. The resulting mRNA contains 5’ UTR, start codon (AUG), coding sequence, stop codon, and 3’ UTR.
    Next is Translation. The ribosome binds the mRNA, it recognizes the start codon (AUG), reads the codons sequentially, tRNA delivers corresponding amino acids. Peptide bonds are formed and it stops at stop codon (UAA, UAG, UGA). The polypeptide then folds, may undergo post-translational modification and could get either secreted or remain intracellular.

    3.5. [Optional] How does it work in nature/biological systems? Describe how a single gene codes for multiple proteins at the transcriptional level.
    Single genes code for multiple proteins through the process of alternate splicing where different combination of exons are expressed.

    Superimposed DNA -> AA

    Part 4: Prepare a Twist DNA Synthesis Order

    RSuperimposed RSuperimposed

    My annotated expression cassette

    (JAX1 protein)[https://benchling.com/s/seq-kczgpR5k4eKn4BIEZYrC?m=slm-XqgAw2klZciZdJUaxluG]

    Final Plasmid

    From Twist Biosciences UI:
    From Twist From Twist

    From Benchling UI:
    From Benchling From Benchling

    Part 5: DNA Read/Write/Edit

    Given my project for Vitiligo to develop a genetic circuit that detects reactive oxidative stress (ROS) and turns on genetic mechanisms to protect melanocytes, I would build the following bioengineering pipeline.

    1. DNA READ → Understand endogenous ROS regulatory DNA
    2. DNA WRITE → Build synthetic ROS-responsive circuit
    3. DNA EDIT → Insert circuit into melanocytes safely

    5.1 DNA Read

    (i) What DNA would you want to sequence (e.g., read) and why? This could be DNA related to human health (e.g. genes related to disease research), environmental monitoring (e.g., sewage waste water, biodiversity analysis), and beyond (e.g. DNA data storage, biobank).

    I would sequence the regulatory DNA that controls the oxidative stress response in melanocytes. My goal is to build a system that detects oxidative stress (ROS) in melanocytes and turn on protective genes. I would want to sequence:

    The endogenous antioxidant response pathway genes in melanocytes
    • Especially NRF2 (NFE2L2)
    • KEAP1
    • Antioxidant genes like HMOX1 (HO-1), NQO1, GCLC

    Out of these, I would choose the NRF2, which is the master regulator of oxidative stress response. It activates antioxidant genes when ROS levels increase. If I understand the exact DNA sequence in melanocytes, I can:
    • Identify natural promoter elements
    • Find antioxidant response elements (AREs)
    • Detect polymorphisms that affect stress response
    • Design a synthetic circuit that mimics or enhances this pathway

    (ii) In lecture, a variety of sequencing technologies were mentioned. What technology or technologies would you use to perform sequencing on your DNA and why?
    Also answer the following questions:

    Is your method first-, second- or third-generation or other? How so?
    What is your input? How do you prepare your input (e.g. fragmentation, adapter ligation, PCR)? List the essential steps.

    Since this is targeted sequencing of specific loci, I would use 2nd-gen, short-read sequencing (Illumina sequencing). Illumina sequencing has high accuracy, is suitable for variant detection. If I were studying structural variants or large rearrangements, I might use PacBio or Oxford Nanopore (third-gen). For my application, short-read high accuracy is ideal.

    What are the essential steps of your chosen sequencing technology, how does it decode the bases of your DNA sample (base calling)?
    Input: Genomic DNA extracted from melanocytes.

    1. DNA Extraction
    • Lysis: Break open cells to release genomic DNA — ensures access to genetic material.
    • Protein digestion: Remove histones and other proteins — prevents contamination and improves downstream efficiency.
    • DNA purification: Isolate clean DNA — required for accurate fragmentation and library prep.
    1. Fragmentation: Mechanical (sonication) or enzymatic shearing: Break DNA into smaller pieces because sequencing platforms cannot read very long DNA directly. Target size ~300–500 bp: Optimal length for Illumina read chemistry and efficient cluster formation.
    2. End Repair: Generate blunt ends: Fix overhangs or damaged ends after fragmentation ensures uniform ends for adapter ligation.
    3. 4. A-tailing: Add single 3′ A overhang: Creates compatible ends for T-overhang adapters which increases ligation specificity and efficiency.
    4. Adapter Ligation
    • Ligate Illumina adapters with index barcodes:
    • Adapters allow DNA fragments to bind to the flow cell.
    • Barcodes enable multiplexing of multiple samples in one sequencing run.
    1. PCR Amplification: Enrich adapter-ligated fragments: Selectively amplifies properly ligated DNA — increases library concentration and removes unligated fragments.
    2. Cluster Generation
    • Bind to flow cell: Adapter sequences hybridize to complementary oligos on the flow cell surface which immobilizes fragments.
    • Bridge amplification: Creates clonal clusters of identical DNA fragments — amplifies signal strength for accurate base detection during sequencing.

    Illumina uses Sequencing by Synthesis (SBS):
    1. Add fluorescently labeled reversible terminator nucleotides.
    2. DNA polymerase incorporates ONE base.
    3. Lasers excite fluorophores.
    4. Camera records color → identifies base.
    5. Terminator removed.
    6. Cycle repeat, where each cycle = one base.

    What is the output of your chosen sequencing technology?
    The output is FASTQ files which contain Sequence reads, Quality scores (Phred scores). This can be used to align to reference genome and perform variant calling

    5.2 DNA Write

    (i) What DNA would you want to synthesize (e.g., write) and why? These could be individual genes, clusters of genes or genetic circuits, whole genomes, and beyond. As described in class thus far, applications could range from therapeutics and drug discovery (e.g., mRNA vaccines and therapies) to novel biomaterials (e.g. structural proteins), to sensors (e.g., genetic circuits for sensing and responding to inflammation, environmental stimuli, etc.), to art (DNA origamis). If possible, include the specific genetic sequence(s) of what you would like to synthesize! You will have the opportunity to actually have Twist synthesize these DNA constructs! :)

    I would synthesize a ROS-sensing genetic circuit that:

    • Detects oxidative stress
    • Activates antioxidant genes
    • Protects melanocytes from damage

    (ii) What technology or technologies would you use to perform this DNA synthesis and why?
    Also answer the following questions:
    I would use Phosphoramidite DNA synthesis + Gene Assembly (Commercial gene synthesis, e.g., Twist Bioscience)

    What are the essential steps of your chosen sequencing methods?
    What are the limitations of your sequencing method (if any) in terms of speed, accuracy, scalability?
    I would use chemical DNA synthesis.

    DNA Synthesis Workflow

    1. Solid-phase phosphoramidite synthesis: Chemically builds short DNA oligos base by base on a solid support to generate designed sequences.
    2. Oligo cleavage: Releases synthesized oligos from the solid support and removes protecting groups to obtain usable DNA.
    3. Oligo assembly (Gibson or enzymatic assembly): Joins overlapping oligos into a full-length gene construct.
    4. Cloning into plasmid backbone: Inserts the assembled gene into a plasmid for propagation and expression in cells.
    5. Sequence verification: Confirms the final DNA sequence is correct and free of synthesis errors.

    Limitations

    • Oligos longer than 200 nt are error-prone: Chemical synthesis efficiency decreases with length, increasing mutation rates.
    • Repetitive elements reduce fidelity: Repeats promote misalignment during synthesis and assembly.
    • GC-rich sequences are difficult: High GC content can impair synthesis and cloning efficiency.
    • Cost increases with length: Longer constructs require more synthesis and validation steps.
    • Cloning validation required: Errors introduced during synthesis must be identified by sequencing.

    5.3 DNA Edit

    (i) What DNA would you want to edit and why? In class, George shared a variety of ways to edit the genes and genomes of humans and other organisms. Such DNA editing technologies have profound implications for human health, development, and even human longevity and human augmentation. DNA editing is also already commonly leveraged for flora and fauna, for example in nature conservation efforts, (animal/plant restoration, de-extinction), or in agriculture (e.g. plant breeding, nitrogen fixation). What kinds of edits might you want to make to DNA (e.g., human genomes and beyond) and why?

    • Edit melanocyte genomic DNA at a safe harbor locus (e.g., AAVS1).
    • This allows stable insertion of a therapeutic construct without disrupting essential endogenous genes.
    • Insert a ROS-responsive antioxidant genetic circuit. This enables melanocytes to activate protective genes only during oxidative stress, reducing unnecessary expression.
    • Optionally enhance endogenous NRF2 pathway activity. Strengthening the native antioxidant response may improve resilience to oxidative damage implicated in vitiligo.

    (ii) What technology or technologies would you use to perform these DNA edits and why?

    I’ll use CRISPR-Cas9 genome editing. This system enables targeted DNA modification at precise genomic locations.

    • Design a single guide RNA targeting the chosen safe harbor locus. The guide RNA determines the exact genomic cut site and ensures specificity.
    • Provide a donor DNA template containing the ROS-sensing circuit with homology arms. Homology arms direct precise insertion via homology-directed repair.
    • Deliver Cas9, guide RNA, and donor DNA into melanocytes ex vivo. Editing cells outside the body improves safety and allows selection of correctly modified cells.
    • Screen and sequence edited clones. Verification ensures accurate insertion and absence of unintended mutations.

    Also answer the following questions:

    How does your technology of choice edit DNA? What are the essential steps?

    • Cas9 introduces a double-strand break at the target site. The break initiates cellular DNA repair mechanisms.
    • Cells repair the break using homology-directed repair when a donor template is present. This enables precise integration of the therapeutic circuit.
    • The edited locus now contains the ROS-responsive construct. The inserted sequence becomes a permanent part of the melanocyte genome.

    What preparation do you need to do (e.g. design steps) and what is the input (e.g. DNA template, enzymes, plasmids, primers, guides, cells) for the editing?

    CRISPR 1 CRISPR 1 CRISPR 2 CRISPR 2 CRISPR 3 CRISPR 3 (Source)[https://www.youtube.com/watch?v=cLMo6DYdJRE]

    • Cas9 protein or expression plasmid. Provides the nuclease that cuts DNA
    • Single guide RNA (sgRNA). Directs Cas9 to the target locus
    • Donor DNA template with homology arms. Supplies the sequence to be inserted.
    • Cultured melanocytes: Serve as the editable cellular substrate.

    What are the limitations of your editing methods (if any) in terms of efficiency or precision?

    • Homology-directed repair efficiency can be low. Precise insertion may occur in only a fraction of treated cells.
    • Off-target edits are possible. Imperfect guide specificity may lead to unintended genomic changes.
    • Delivery into primary melanocytes can be challenging. Some cell types are difficult to transfect efficiently.
    • Permanent genomic edits raise regulatory and safety concerns. Long-term monitoring would be required before clinical use.

    Week 3 HW: Opentrons and automation tools

    Find and describe a published paper that utilizes the Opentrons or an automation tool to achieve novel biological applications.

    Semiautomated Production of Cell-Free Biosensors
    https://www.sciencedirect.com/org/science/article/abs/pii/S2161506325000725

    Cell-free biosensors combine the gene expression machinery of cells with engineered genetic circuits, enabling detection of molecules through measurable outputs like fluorescence (GFP) or color change (LacZ). These systems have unique advantages - they can be freeze-dried, distributed cheaply, and used at the point of need without living cells, making them promising platforms for environmental and health diagnostics. However, traditional workflows rely on manual pipetting to assemble reactions, which is slow and introduces variability in performance.

    To overcome this bottleneck, the authors developed and evaluated a semiautomated manufacturing protocol using the Opentrons OT-2 liquid handling robot. They compared traditional manual assembly of reactions with an automated protocol and demonstrated the approach by constructing a full 384-well plate of fluoride-sensing cell-free biosensors. The reactions assembled by Opentrons performed comparably to expectations from manual assembly, supporting the idea that liquid-handling automation can improve scalability, reproducibility, and quality control in biosensor production.

    Write a description about what you intend to do with automation tools for your final project. You may include example pseudocode, Python scripts, 3D printed holders, a plan for how to use Ginkgo Nebula, and more. You may reference this week’s recitation slide deck for lab automation details.

    One of my ideas is to build a Programmable Regenerative Biofilter for Selective VOC Destruction
    I would use the cloud lab to answer:

    • Which detector design is most sensitive? Test 30-100 versions the promoter (the “on switch” strength), the regulator amount, the reporter (GFP glow vs luciferase glow)
    • Which enzyme destroys formaldehyde fastest?
    • Which setup lasts the longest before it wears out?

    Find the best formaldehyde detector (it glows only when formaldehyde is present). Then find the best enzyme that destroys formaldehyde. Then test how to glue that enzyme onto a filter material so it works in a cartridge. Finally, combine detection and cleanup into a system that turns itself on only when formaldehyde is in the air.

    Automated Build/Test Pipeline (Formaldehyde Focused):

    1. Design & DNA Assembly (Build)
    Upload formaldehyde sensor variants and enzyme gene sequences to the cloud lab → automated DNA synthesis, Gibson assembly, transformation, and sequence verification.

    2. High-Throughput Sensor Screening (Test)
    Express sensor constructs in 96-well cell-free reactions → expose to a formaldehyde concentration gradient → measure fluorescence to identify lowest detection threshold and highest signal-to-noise ratio.

    3. Enzyme Activity Optimization (Test)
    Express candidate formaldehyde-degrading enzymes in cell-free → add formaldehyde substrate → quantify degradation rate via colorimetric or absorbance assay → rank by turnover and stability.

    4. Immobilization & Stability Assay (Build/Test)
    Attach top enzyme candidates to bead or hydrogel matrices → wash and stress-test (heat, humidity simulation) → measure retained catalytic activity over time.

    5. Closed-Loop Integration Test (Build/Test)
    Combine best sensor + enzyme modules in automated plate workflow → confirm: formaldehyde detection triggers enzyme expression → formaldehyde concentration decreases over time → quantify response dynamics and regeneration capacity.