Tutorial: Finding the Genes that code for Diseases

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Tutorial Finding the Genes that code for
Diseases

• When the arrow buttons appear, use them to move
  forward through the tutorial.
• Click on your mouse to move through animations.

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DNA CHIPS!

• How do we know the DNA sequence of the genes for
  certain diseases?
• How do scientists discover which genes are
  present in diseased tissue?

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What is a DNA Chip?

• DNA chips are made of millions of copies of DNA
  Probes.
• The probes are fixed on a solid support like a
  glass slide.
• Click on the slide to zoom in.

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What is a DNA Chip?

• Each spot on the microarray has millions of
  copies of a different DNA probe
• Click on a probe to see it more closely

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What is a DNA Chip?

• DNA Probes are single stranded molecules each
  representing one gene.
• Click on the probe DNA strand to find its
  complementary sequences.

T T A G G C C
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What is a DNA Chip?

• Select the Probes complimentary sequence
• TTAGGCC
• AAUCCGG
• UUAGGCC
• AATCCGG

T T A G G C C
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Oops!

• We are looking for the complimentary DNA
  sequence.
• Click Here to Return to the Question

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What is a DNA Chip?

• Thats right!
• Probes hybridize with complementary sequences

T T A G G C C
A A T C C G G
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What is a DNA Chip?

• Each spot on the DNA chip has a different probe
  for known genes.
• Click here to see how we use those known genes to
  find unknown genes.

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Continue clicking to see in detail, how DNA from
cancerous and non cancerous breast tissue is
applied to this chip.
1500 Human Genes
65,000 probes on the chip
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Labeled cDNAs are applied to the chip
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Such binding indicates that the gene represented
by the chip DNA was active in the sample.
The tagged cDNA will bind with any complementary
probe.
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The microarray is scanned and a computer shows
the amount of gene activity with a color read out
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Present in Non- Cancerous Tissue
Present in Both
Present in Cancerous Tissue
Click on any one of the spots that represents a
gene that could cause breast cancer.
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These 6 genes appear in cancerous breast tissue
and do not appear in non-cancerous tissue.
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DNA Chips Find DNA Sequences

• This data from DNA chips helps scientists to
  discover the genes for breast cancer and other
  diseases.