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Microarrays
Gene Expression
• Except gametes, every one of our
cells contains 46 chromosomes.
• There are about 30,000 genes
found on these chromosomes.
• Some genes are active on every
chromosome in every cell.
• Some genes are active only in
certain cells
Normal Male Karyotype
Normal Male Karyotype
PINK1 gene – Active in
every cell in the body
CASQ2 gene – Active in
only cardiac muscle cells
ACTA1 gene – Active in
skeletal muscle cells
Changes in Gene Expression
• May be caused by
the environment
• May indicate disease
progression
• May highlight
differences among
individuals
What’s a microarray?
• Allow scientists to analyze the expression of
many genes in a single experiment.
What does it do?
• Compare gene expression in healthy and
sick people
• Compare gene expression of the same
organism during different life stages
• Compare gene expression of the same
organism in different environments
How does it work?
Single stranded
probes search for
complementary target
sequences.
Probe sequence
target sequence
What a microarray looks like
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Glass slide, silicon chip, or nylon membrane
1.25 cm x 1.25 cm checkerboard
Each square is 11 micrometers by 11 micrometers
Attached to each square are millions of copies of one
of a single stranded DNA probe
Human Genome Array
• The size of a dime
• Over 1.3 million
squares
• Can screen for the
presence of 47,000
different nucleic acid
sequences
How to make a microarray?
Patient 1:
Patient 2:
Microarray:
Interpretation:
Genes A and B are expressed in healthy
people
Genes B and D are expressed in sick people