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Karyotype Lab
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Homologous pairs Sex linked inheritance Karyotype--A key to the study of Sex Linked Inheritance Karyotype--A key to the study of Sex Linked Inheritance
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Prenatal diagnosis: Trisomy 21 (Down’s syndrome) karyotype picture of the chromosomes in a cell used to check for abnormalities Organized from largest to smallest
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Preparing a karyotype harvest cells Postnatal diagnostic karyotype tumor biopsy skin cells from mouth (ie. for non-cancer related diagnoses) Prenatal diagnostic karyotype chorionic villi sampling (CVS) amniocentesis
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Chromosomes 46 Chromosomes in each cell – 6 feet of DNA in each cell – DNA is built around histones (coiling into nucleosomes) X chromosome = 1400 Genes Y Chromosome = 200 Genes
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Centromere Centromere helps distinguish between chromosomes – Metacentric – Centromere is located so that the p and q arm are similar in length – Acrocentric – centromere is located so that one arm is shorter then the other – Submetacentric – centromere is slightly off center
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Chromosome Structure p-arm = shorter arm q-arm = longer arm
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Prenatal diagnosis: amniocentesis sampling cells from amniotic fluid usually done ~ 15-18 weeks
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Prenatal diagnosis: chorionic villi sampling (CVS) sampling cells from placenta usually done 10-12 weeks
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Preparing a karyotype harvest cells culture cells 1-2 days arrest cells in metaphase with colchicine A chemical that stops cell division during metaphase (crack nucleus to view chromosomes) metaphase
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MITOSIS DNA replication chromosomes condense nuclear envelope breaks down chromosomes aligned on spindle fibers
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Preparing a karyotype harvest cells culture cells 1-2 days arrest cells in metaphase with colchicine “spread” cells on slide and stain count chromosomes in 20 representative cells capture image of 5 “best” cells and construct karyotypes for each metaphase
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metaphase spread chromosomes stained with DAPI, a fluorescing stain that specifically binds double stranded DNA FISH analysis of chromosomes: Fluorescent IN SITU hybridization
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DiGeorge syndrome/CATCH22 microdeletion on chromosome 22 birth defect that affects the immune system absence of or underdevelopment of the thymus and parathyroid glands facial features include low-set ears, wide-set eyes, small jaw, and bowing up of upper lip
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FISH tests: DiGeorge syndrome Expose DAPI-stained chromosomes to mixture of fluorescent probes green = control probe for chromosome 22 red = probe for DiGeorge region on long arm of chromosome 22
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FISH tests: Painting chromosomes Expose chromosomes to fluorescent probes that highlight entire chromosomes
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Comparative Genomic Hybridization Allow for measurement of change in DNA copy number at gene level. Same as performing thousands of FISH simultaneously.
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Deletion
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Duplication
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Inversion
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Translocation
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Directions! 1.Work in pairs 2.Obtain the following: 1.Case study 2.Karyotype 3.Correctly Place Karyotypes 4.Make a prognosis of the patient 5.Obtain a computer 6.Research the disorder 7.Prepare a short presentation (using ELMO) for tomorrow 1.Discuss patient and disorder 2.Symptoms 3.Treatments 4.Quality of Life
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