Genetics of Disease (Medical Interventions) · Tuesday, September 15, 2026 · 80 minutes
Compare two BLAST hits: E-value and query coverage
One two-hit comparison table and a revised, qualified statement citing percent identity, E-value and query coverage.
This page has four parts, in the order you use them. Part 1 is what you need to know: five definitions and one rule. Part 2 says what to do, in plain English. Part 3 shows the comparison done once on supplied practice values. Part 4 is your own table and statement. Everything you write goes on one page.
Start: Part 1, then follow the steps in Part 2. Digital deadline: September 15, 11:59 PM.
Part 1 of 4 · Background and definitions
What you need to know before you write
Where you are: On Monday, you saved your input source, search settings and actual result or unfinished step. Reopen that record. The tutorial checked the workflow; it did not validate the case identification.
The question you are answering: What do the recorded numbers support about two compared hits, and what remains uncertain?
Read these definitions before comparing the rows. Keep each result's actual column label and comparison context. Part 2 sends you here in step 2, and every row of your table in Part 4 uses these five words.
- Query
- The input sequence being compared with database entries.
- Hit
- A database entry returned with an alignment to the query.
- Percent identity
- The percentage of positions in the reported alignment with identical letters. It does not describe unaligned parts of the query.
- Query coverage
- The percentage of the query represented in the alignment or alignments reported for that hit. Keep the actual column label and comparison context.
- E-value
- The expected number of alignments with that score or better arising by chance for that database search. It is an expected count, not a probability or percent.
The notation aid
2e-60 means 2 × 10^-60. Retain the recorded notation. Do not round a small value to zero or turn it into a diagnostic probability.
Smaller E-values indicate greater statistical significance in the relevant search context. No universal cutoff or disease-identification guarantee follows.
The one rule for today: the three-measures rule
Read percent identity, query coverage and E-value together before writing a qualified comparison. That is the whole rule, and steps 4 and 5 in Part 2 apply it: no single number decides a comparison.
The mistake to avoid: One strong-looking number proves an organism's identity. Percent identity describes aligned positions. Use all three recorded measures and context, and keep the conclusion within the stated limit.
The limit that applies to everything today
The comparison cannot establish an organism's identity, a diagnosis or a disease cause. If actual measures conflict or information is missing, state what remains uncertain instead of forcing a winner.
Part 2 of 4 · Directions in plain English
What you will do today, in order
Compare two recorded hits using percent identity, E-value and query coverage, then write a qualified statement that matches the evidence.
Six steps. Each one says what to do, and the line under it says where on this page the material lives.
Step 1. Choose two usable hits from your saved Monday record. If unavailable, use the supplied A/B illustrative practice and label that route. Keep the actual missing or unfinished step noted separately in the same record.
Where: 4.1 Your evidence route.
Step 2. Read the definitions of query, hit, percent identity, query coverage and E-value. Use the notation aid before copying a small E-value.
Where: Part 1, the five definitions and the notation aid.
Step 3. Fill both rows of the comparison table from the chosen evidence. Keep the source and context with the actual column labels. Do not invent a missing value.
Where: 4.2 Your table.
Step 4. Compare percent identity, query coverage and E-value together. Explain what the recorded measures support. If the measures conflict or information is missing, state the uncertainty instead of forcing a winner.
Where: 4.2 Your table, then the statement.
Step 5. Revise the statement so it cites all three recorded measures and stays within the claim limit. Keep illustrative practice separate from an actual search result.
Where: 4.2 The statement.
Step 6. Check the two rows, source label and statement. Submit one PDF through assignment 8520302476, unless your paper was collected in class. Keep the record for later work.
Where: Turn in.
Use the optional guided notes if they help. Read one work plan, not all three. If a required file or step is unclear, tell Mr. Mendoza which step you reached. Use the supplied A/B practice when your actual record is unavailable; label it honestly and keep the unfinished-investigation note.
The 80-minute plan
- 0-10 min: Reopen Monday's record and choose actual hits or the labeled A/B practice route.
- 10-25 min: Read the five definitions and notation aid. Locate each measure in the supplied example.
- 25-40 min: Fill both rows from the same chosen evidence context. Check the recorded values.
- 40-55 min: Compare all three measures. Discuss disagreement or missing information without forcing a winner.
- 55-70 min: Revise the qualified statement using the recorded measures and claim limit.
- 70-80 min: Check the source label, two rows and statement; submit the same product once and keep the record.
Slides and optional guided notes
The slides follow the same order as this page. Use the deck and optional guided notes for the same two-hit table and qualified statement. No extra exit ticket or group product is due.
Part 3 of 4 · Worked example
A and B: the comparison done once
Illustrative practice values, not a BLAST run or case result. Assume the same illustrative comparison context for A and B. No sequence, organism or disease is supplied. Read it for the order of the work, because Part 4 asks for the same order with your own two hits: copy the three measures for each hit, compare all three together, then write a statement that stays inside the limit.
The supplied practice values
| Hit label | Percent identity | E-value | Query coverage |
|---|---|---|---|
| A | 99% | 2e-60 | 98% |
| B | 99% | 0.4 | 11% |
What a finished statement looks like
Illustrative practice values, not a BLAST run or case result. In the same illustrative comparison context, A and B both have 99% identity. A has greater query coverage (98% versus 11%) and a smaller E-value (2e-60 versus 0.4), supporting a stronger reported sequence-similarity comparison for A. This does not establish an organism's identity, a diagnosis or a disease cause.
The blank statement frame you will fill
From [actual saved record or supplied illustrative practice], [hit labels] have [recorded identity], [recorded E-value] and [recorded coverage]. These measures support [qualified comparison, or why the comparison remains uncertain]. [State a limit.]
Do not copy A and B into your case work. This completes the local comparison-practice product only. It does not record a successful search, finish the missing Monday activity or certify official PLTW completion.
Open this example on its own pagePart 4 of 4 · Your work
Your evidence route, your table and your statement
Everything below is yours to write. First choose which evidence you are comparing. Then fill the two-row table, and write the statement under it. One page, submitted once.
4.1 Your evidence route
Route 1: your own Monday record
Use two usable hits from your own saved Monday record. Keep the input source and actual search settings with the table. Copy the recorded values without guessing.
Route 2: the supplied practice
If your Monday record is unavailable or has fewer than two usable hits, use supplied illustrative hits A and B for the same table and statement. Label your work “Skill practice using supplied illustrative values”. Note your actual missing or unfinished investigation step separately in the same PDF.
If actual measures conflict or information is missing, state what remains uncertain instead of forcing a winner.
4.2 Your table and statement
F1 is the blank record layout, not search data. Fill both rows from the one evidence context you chose in 4.1.
| Hit label | Percent identity | E-value | Query coverage |
|---|---|---|---|
| [first hit] | [recorded value] | [recorded value] | [recorded value] |
| [second hit] | [recorded value] | [recorded value] | [recorded value] |
- Evidence route: actual record or skill practice: ____________________
- Source and comparison context: ____________________
- Actual database/program settings for actual records: ____________________
- Missing or unfinished investigation step, if applicable: ____________________
Qualified statement: ____________________
Write the statement with the frame from Part 3: From [actual saved record or supplied illustrative practice], [hit labels] have [recorded identity], [recorded E-value] and [recorded coverage]. These measures support [qualified comparison, or why the comparison remains uncertain]. [State a limit.]
4.3 Check before you turn in
- Record two hits with all three measures and their source/context.
- Explain the comparison using the supplied definitions and a stated limit.
- Submit one labeled comparison product without claiming practice is an actual search.
Turn in one page
Submit the table and revised statement together as one PDF to Schoology assignment 8520302476 by Tuesday, September 15 at 11:59 PM. If your paper was collected in class, do not upload it again. Keep your original record.
Keep this comparison record for later work.
Help when you need it
Need help? Choose a starting point
Restart where you stopped
Choose your evidence route first: two usable hits from Monday, or supplied A/B skill practice. Then fill both table rows, compare the three measures and revise the same statement. Do not switch to a different task.
A smaller first step, or a step further
Start smaller: Read these definitions before comparing the rows. Keep each result's actual column label and comparison context. 2e-60 means 2 × 10^-60. Retain the recorded notation. Do not round a small value to zero or turn it into a diagnostic probability.
If you finish: Optional: explain what remains uncertain in the same comparison. Add no new numerical result or separate submission.
Check yourself
Illustrative practice values, not a BLAST run or case result. Compare A and B in the supplied table. What do their recorded measures support, and what do they not establish?
Show the answer
Illustrative practice values, not a BLAST run or case result. In the same illustrative comparison context, A and B both have 99% identity. A has greater query coverage (98% versus 11%) and a smaller E-value (2e-60 versus 0.4), supporting a stronger reported sequence-similarity comparison for A. This does not establish an organism's identity, a diagnosis or a disease cause.
Connection to PLTW
Original local comparison practice connected to PLTW MI Activity 1.1.3. Official materials remain in the class hub. Completing this practice does not certify official PLTW completion.
Today's stopping point: Complete today's local comparison practice. Do not claim a new search, missing Monday work or the full official activity is complete.
Course connection
- Activity 1.1.3 Using DNA to Identify Pathogens