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18 Cards in this Set
- Front
- Back
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standard evaluation
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-blood needs to be put into culture
-then you harvest - get blood from bottom of a flask and put it on the microscope -fixation -analyze 20 metaphase spreads -form a karyotype |
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routine banding and special banding
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-G-banding (giemsa-trypsin-giemasa)
take trypsin, denature the DNA then take giemsa to stain the background -dark bands- genes less active -c-banding: -denature all DNA except the centromere and use barium hydroxide -silver staining (NOR) |
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chromosome classification
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-size, position of centromere, and banding pattern
-metacentric, submetacentric, acrocentric (no short arm-p, all genetic material is on long arm-q) -1 band can represent b/t 50-100 genes |
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nomenclature
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-chromosome modal number
-sex chromosomes -numerical or structural abnormalities, list in numerical order ex. 45,X,t(2;4)(p11;q13),t(7;21)(p13;q12) |
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down syndrome
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-trisomy 21 (extra chromosome 21)
-most common form of mental retardation |
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patau syndrome
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-trisomy 13
-cleft lip and palate -polydactyly of hands and feet -congenital heart defects -mental retardation |
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turner syndrome
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-45X
-short stature -short webbed neck -low set ears -wide carrying angle -normal intelligence -sterile |
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Klinefelter Syndrome
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-47XXY
-gynecomastia -sterile -taller -testicular atrophy |
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deletion syndromes
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- These syndromes are all missing portions of specific chromosomes, which result in the characteristic phenotype of each syndrome
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Prader-Willi Syndrome (PWS)
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-Results from a deletion of chromosome 15q11-q13 on the paternal chromosome
-Hypotonia, hypogonadism, hyperphagia, hypomentia -almond eyes, small hands and feet, short -caused by del (15) (q11-q13) |
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FISH
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-enables genetic analysis of many sample types
-rapid, straightforward result interpretation -take pt DNA and take probe of the region in question -denature DNA -let them reaneal -if gene is present it will light up -used to ID chromosomes, aneuploidy detection, centrome analysis, unique sequences, gene amplification, interphase analysis, cancer cytogenetics, transolocation ID etc. |
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Direct amniocentesis
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-direct interphase analysis results are preliminary
-Structural abnormalities, mosaicism, and numerical abnormalities of other chromosomes (i.e., other than 13,18,21,X and Y) cannot be detected by prenatal direct FISH analysis -LIMITATIONS: screening for only 5 chromosomes (X,Y,13,18,21); will not detect aneuploidy or structural rearrangements involving all other chromosomes |
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Subtelomere analysis
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-subteleomere deletions are seen in 5-10% of pts with nonspecific mental retardation, developmental delay and autism
-however, 1% pf pop may be carriers of variant subtelomeres! -parental F/u studies are necessary |
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Comparative genomic hybridization (CGH)
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-take sample DNA and take control
-label 1 red, 1 green -hybridize it onto a metaphase spread -use computer analysis to determine amts of DNA (amplification-to rt of grid and deletions) |
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limitations of CGH
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-resolution limited to regions of the genome greater than 10-20 Mb
-balanced rearrangements- NOT detected -so always need to do chromosomes |
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chromosome microarray analysis
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-tells you about all the chomosomes
-looking at amts of DNA -put sample onto a platform that has sequences mapped throughout the genome -anything yellow--> equal amts of DNA -Green --> amplified; Red--> deleted -limitations: gain or loss of genomic material; will not detect: balanced translocations, inversions, low level mosaicism, point mutation |
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clone
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-a cell population derived form a single progenitor
-at least 2 cells that have the same structural aberration -at least 3 cells that have the same numerical aberration -the # of cells that consititute the clone is given in brackets after the karyotype ex. 46,XX, t(8;21)(q22; q22) [23] |
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Spectral Karyotyping (SKY)
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-labeling each homologue a different color and looking at the rearrangement of chromosomes
-used for cancer cytogenetics -computer lays out the colors and it helps you karyotype -good way to determine chromosome abnormalities in cancer |
