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Detecting DNA with DNA probes
arrays
• DNA sequences can be detected by DNA
probes and arrays (= collection of microscopic
DNA spots attached to a solid surface)
• DNA probes are pieces of DNA used to detect
the presence of specific sequences in DNA.
(Do not get probes mixed up with the primers
used in PCR.)
• What characteristics will DNA probes need to
have?
DNA probes are:
•
•
•
•
Made of DNA
Short
Single stranded
Complementary to the sequence being
searched for
• Labelled with fluorescent or radioactive
markers to allow detection
Example 1: Using DNA probes to search a match on an
organism’s DNA
(N.b. 1: This is not an array
N.b. 2: This corresponds to the example in the printed notes)
Example 2: using DNA probes for microarrays
(see book p74)
(array= collection of microscopic DNA spots attached
to a solid surface)
Microarray
Small sections of genomic DNA as
microscopic spots fixed onto a
surface as an orderly collection
Microarrays can be used to study the expression
of genes and compare patterns between healthy
and unhealthy cells.
It is the mRNA from cells which is used to form
labelled probes (after it has been copied into
single stranded DNA).
(To compare gene expression in
healthy and diseased cells)
Fluorescent labeling
(To obtain DNA from the
RNA because it will
hybridize better to the DNA
on the array
(To be able to see
When the DNA has
hybridized to the
DNA fixed on the array)
• DNA probes can be used to detect:
– Single gene mutations
– Changes in gene expression due to disease
(microarray)
• Questions:
• Booklet p15: 1
• Book q 2&3 p76 + What you should know.