Chapter 5: Genomic Imprinting

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Chapter 5 Genomic Imprinting (pp 101-102
120-121) Uniparental Disomy (p 253)
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• Genomic Imprinting
• The differential expression of a gene -
• depending on whether the chromosome is
• inherited from the mother or father.

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A marking process - chemical tags (-CH3 groups)
on the DNA, mark gene as maternal or paternal
block transcription (inactivates that gene).
CH3
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a single gene may be tagged as maternal
or paternal OR a part of a
chromosome, an entire chromosome
(houseflies) all chromosomes from one parent.
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Chromosome marked before egg/sperm
production. Tag remains throughout the
organisms life in each somatic cell it
influences gene function is erased during
gamete production. A new imprint is put on
gametes. Modifies DNA but is NOT a mutation.
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Two different diseases a result of imprinting
in the same chromosomal region. What
determines which disorder appears?
CH3
CH3
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Uniparental Disomy In 40 of PWS cases - no
deletion Using molecular techniques find
both 15 chromosomes are paternal
CH3
CH3

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Uniparental Disomy
50 of Anglemans Syndrome cases - no
deletion in 15
Molecular Analysis both chromosomes are
maternal
CH3
CH3
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Other examples of imprinted loci
Beckwith-Weidemann Syndrome (11) Wilms
Tumor (11) Cystic Fibrosis (7) Turners
Syndrome (XO) Retinoblastoma (13)
Osteosarcoma
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Birth Weight Genomic Imprinting
IgF2 (insulin-like growth factor II) H19
(a nearby gene, paternally imprinted).
Paternal IgF2 expressed get fetal
placental growth
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