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20 Cards in this Set
- Front
- Back
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-Trisomy
-Monosomy -Triploidy |
Trisomy: copy of one chromosome
Monosomy: loss of one copy of a chromosome -only one full monosomy known. 45, X Triploidy: 3 copies of every chromosome (most often two sperm fertilizing one egg) |
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NOMENCLATURE:
-Balanced -Unbalanced -Robertsonian |
-Balanced:
46,XX,t(10;11)(p15;q21) -Unbalanced: 46,XX,der(10)t(10;11)(p15;q21) -Robertsonian: 45,XX,der(13;14)(q10;q10) |
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What are the acrocentric chromosomes? What occurs between them?
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-13/14/15/21/22
-Robertsonian translocations |
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If mother is 46,XX,t(10;11)(p15;q21).... what are the possible genotypes for the fetus?
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-46,XX,der(10)t(10;11)(p15;q21)
OR der(11) -46,XX,t(10;11)(p15;q21) -46,XX |
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If the mother is 45,XX,der(14;21)(q10;q10)... what are the possible genotypes for the fetus?
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-46, XY
-45,XY,der(14;21)(q10;q10) -46;XY,der(14;21)(q10;q10),+14 OR +21 |
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Aquired change: t(9;22)
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•First cancer described, shown to be balanced translocation t(9;22)(q34;q11.2)
o Seen in 90-95% of cases of chronic myeloid leukemia (CML) •Do FISH assay to determine break points (overlapping break points = yellow) |
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Constitutional vs. Acquired:
-Trisomy & origin of trisomy -monosomy -translocation: balanced -translocation: unbalanced -where |
-Trisomy
Constitutional: 13,18,21..Meiosis Acquired: Any...Mitosis -Translocation: balanced Constitutional: no impact on phenotype, unique to family Acquired: Diagnostic, recurrent -Translocation: unbalanced Constitutional:abnormal phenotype Acquired: normal phenotype -Where? Constitutional: Majority of cells Acquired: Site of cancer |
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Breakpoints of acquired translocations tend to occur where?
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Breakpoints of acquired translocations occur at the oncogenes, genes involved in driving cell cycle
Acquired deletions occur at genes involved in control of cell cycle (tumor suppressor genes) |
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Mendel's Laws
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-Unit Inheritance: parental phenotypes do not blend
-Segregation: genes occur in pairs; only one member of pair is transmitted -Independent assortment: genes at diff. loci are transmitted independently |
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AD characteristics on pedigree
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-transmission vertical
-only one copy necessary for expression -MALE TO MALE TRANSMISSION -unaffected individuals have unaffected children |
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AD clinical characteristics
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-variable expressivity
-penetrance -variation in age of onset -occurence of new mutations |
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AR pedigree characteristics
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-two copies needed for expression
-both parents carriers -family history may be neg. -consanguinity may be present |
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AR clinical characteristics
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-AR disorders sometimes cluster geographically
-penetrance is usually complete w/ little phenotypic variability |
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X-linked Recessive Disorders pedigree
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-hemizygous males affected
-het females fine -incidence much higher in males -NO MALE TO MALE TRANSMISSION |
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How can X-linked recessive disorders occur in females?
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-cells w/ normal X inactivated
-affected female w/ 45, X karyotype OR X chromosome deletion of normal gene & inactivation of X -affected female w/ affected mother & father (rare) |
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Lyon hypothesis
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-only one X active in females
-inactivation occurs early on |
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X-linked dominant inheritance pedigree
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-disorders generally seen in females
-lethal in males -rare |
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Key to mitochondrial inheritance pedigree
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-males children fine
-affected females children NOT OK |
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-heteroplasmy
-homoplasmy |
-heterplasmy: mtDNA is mixture of normal & mutant forms
-homoplasmy: mtDNA is all the same type |
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mitochondrial threshold effect
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certain percentage of abnormal mtDNA tolerated, there is critical threshold
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