Read A Microarray

Read an expression microarray: each spot is a gene; the signal color tells you if it is up- or down-regulated versus a reference.

Builds on (2 levels back)inferred · high confidence

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Prerequisites are inferred: pending teacher review.

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

Read a microarray by matching each spot's color to the rule: red = up-regulated, green = down-regulated, yellow = unchanged.

Step 1: Read the color key

Use the table: red = up-regulated (the gene is more active than the reference), green = down-regulated (less active), yellow = unchanged (about the same).

Gene spot	Signal color	Color rule
Gene 1	red	red = up-regulated (more active)
Gene 2	green	green = down-regulated (less active)
Gene 3	yellow	yellow = unchanged vs reference
Gene 4	red	red = up-regulated (more active)

Step 2: Go spot by spot

For each gene spot, find its color in the table, then say up, down, or unchanged. Do not guess from the gene's name or position.

Step 3: Name the limit

A microarray shows that a gene's activity changed, but it does not by itself prove what caused the change or what the protein does.

Practice

Use the microarray table. Which gene is up-regulated (more active than the reference)?

Reviewed

Gene spot	Signal color	Color rule
Gene 1	red	red = up-regulated (more active)
Gene 2	green	green = down-regulated (less active)
Gene 3	yellow	yellow = unchanged vs reference
Gene 4	red	red = up-regulated (more active)

A.Gene 1
B.Gene 2
C.Gene 3
D.No gene is up-regulated

Show the worked solution ▾

Answer: A. Gene 1

Step 1: Apply the color rule: Red means up-regulated. Find the red spots in the table.
Step 2: Read each row: Gene 1 is red (up), Gene 2 is green (down), Gene 3 is yellow (unchanged). Gene 1 is the up-regulated one listed in the options.

Why it's right: Gene 1's spot is red, and the table's rule says red = up-regulated.

Why the others miss:

B: Gene 2 is green, which is down-regulated.
C: Gene 3 is yellow, which is unchanged.
D: Gene 1 (red) is up-regulated, so at least one gene is.

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

Where you'd see this

A lab reads a cancer-vs-normal microarray and circles every red spot as a gene turned up in the tumor.

Careers that use this

Molecular Technologist: Reads microarray colors to report which genes are turned up or down in a sample.

Video library

Watch: Read A Microarray

Hybridization (microarray) | Biomolecules | MCAT | Khan Academy

khanacademymedicine · ~9 min

Guided notes

Fill these in as you work through the lesson.

Big idea: On a microarray each spot is a gene, and the spot's color tells you whether the gene is up-regulated, down-regulated, or unchanged compared with a reference.

Key terms: write the meaning

Microarray (grid of spots, one gene per spot):
Up-regulated (gene more active (red)):
Down-regulated (gene less active (green)):
Reference (the sample you compare against):

The rule

On a microarray, a red spot means the gene is , a green spot means the gene is , and a yellow spot means the gene is unchanged.

Check yourself

What does one spot on the array stand for?
Which color means more active, and which means less active?
What can the array NOT prove on its own?

Work one example

Using the table, list which genes are up-regulated and which are down-regulated, then write one sentence on what the array cannot prove.