John Hay
John Hay Biomedical
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Genetics of Disease (Medical Interventions)
Unit 2: Unit 2.1 Genetic Testing & ScreeningMI 2.1Bio-Molecular Technology

Interpret SNP Data

Read a SNP table: compare alleles across people to find where two individuals differ or which SNP tracks a trait.

Builds on (2 levels back)inferred · high confidence
  • DNA/RNA base pairing: Sequence and codon tasks depend on reading bases in order.
  • Read a genetics model: Pedigrees, karyotypes, and charts are models that need a key.

Prerequisites are inferred: pending teacher review.

Re-learn the skill with worked practice and clear examples.

Interpret a SNP table by comparing alleles across people to find where two individuals differ.

Step 1: Read the table
Each row is a SNP (rs-ID); each column is a person. The letters are the alleles each person carries.
SNP (rs-ID)AnnaBenCarl
rs101AGA
rs202CCC
rs303TTG
SNP allele comparison table for three people
Step 2: Compare across a row
To see where two people differ, scan a row and check whether their letters are the same or different. Different letters mean they differ at that SNP.
Step 3: Name the limit
A difference at a SNP shows the people carry different alleles there; it does not by itself prove that SNP causes any trait or disease.
Practice

Use the SNP table. At which SNP do Anna and Ben have different alleles?

Reviewed
SNP (rs-ID)AnnaBenCarl
rs101AGA
rs202CCC
rs303TTG
SNP allele comparison table for three people
  1. A.rs101
  2. B.rs202
  3. C.rs303
  4. D.They are identical at every SNP
Show the worked solution ▾

Answer: A. rs101

  1. Step 1: Compare Anna and Ben row by row: rs101: Anna A vs Ben G (different). rs202: C vs C (same). rs303: T vs T (same).
  2. Step 2: Pick the differing row: Only rs101 shows different letters for Anna and Ben.

Why it's right: At rs101 Anna has A and Ben has G, so their alleles differ there; at rs202 and rs303 they match.

Why the others miss:
  • B: At rs202 both Anna and Ben have C, so they match.
  • C: At rs303 both Anna and Ben have T, so they match.
  • D: They differ at rs101, so they are not identical.

Aligned to Bio-Molecular Technology · reading level ~grade 9

Where you'd see this
  • A lab compares two patients' SNP rows to find the single spot where their DNA letters differ.
Careers that use this
Genetic Counselor: Compares people's SNP alleles to see exactly where their DNA differs before discussing risk.
Video library
Watch: Interpret SNP Data
Hybridization (microarray) | Biomolecules | MCAT | Khan Academy
khanacademymedicine · ~9 min
Guided notes

Fill these in as you work through the lesson.

Big idea: A SNP table lists the allele each person carries at each single-base spot, so you can compare people to find where they differ or which SNP lines up with a trait.
Key terms: write the meaning
  • SNP (single DNA-letter difference (rs-ID)):  
  • Allele (the DNA base a person has at a spot):  
  • rs-ID (the name of a SNP (like rs101)):  
  • Tracks a trait (allele pattern matches who has the trait):  
The rule

Read a SNP table by going across a   to compare two people; a SNP tracks a trait when its   pattern matches who has the trait.

Check yourself
  1. What does each letter in the table stand for? 
  2. At which SNP do two named people differ? 
  3. Which SNP's pattern matches who has the trait? 
Work one example

Using the table, name one SNP where two named people differ, then say which SNP could track a trait and why that is only a lead.