Karyotype Lab

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

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

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

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

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

Chromosome Structure p-arm = shorter arm q-arm = longer arm

Prenatal diagnosis: amniocentesis sampling cells from amniotic fluid usually done ~ weeks

Prenatal diagnosis: chorionic villi sampling (CVS) sampling cells from placenta usually done weeks

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

MITOSIS DNA replication chromosomes condense nuclear envelope breaks down chromosomes aligned on spindle fibers

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

metaphase spread chromosomes stained with DAPI, a fluorescing stain that specifically binds double stranded DNA FISH analysis of chromosomes: Fluorescent IN SITU hybridization

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

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

FISH tests: Painting chromosomes Expose chromosomes to fluorescent probes that highlight entire chromosomes

Comparative Genomic Hybridization Allow for measurement of change in DNA copy number at gene level. Same as performing thousands of FISH simultaneously.

Deletion

Duplication

Inversion

Translocation

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