Lecture 8

Lecture 8 - Lecture #8- Cytogenetics, Chromosomal...

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Lecture #8- Cytogenetics, Chromosomal Aberrations and Human Disease (ch 7 p. 156-157; ch 6 p. 120-145) Part I: Cytogenetics: the study of chromosomes and their behavior in a cell. I. Examining human chromosomes A. Chromosomes have distinctive banding patterns when treated with dyes (figures 6.4, 6.5, 6.8) Main dye = Giemsa (produces G-banding) Cytogeneticists identify disrupted banding patterns B. Nomenclature of Chromosomes and their parts Classifications (figure 6.5 again): Whole Chromosome: centromere location, chromosome size and banding pattern. Characterized into 7 groups (A-G) Centromere location designations : Metacentric, submetacentric, and acrocentric 1 chromosome number Q long arm 2 region .4 band Chromosome Arms: Separated by the centromere p (short) and q (long) Chromosome Regions: numbered starting at the centromere Chromosome Bands: within each region. Numbered in the direction away from the centromere. C. Analyzing karyotypes 1. Visible chromosomal aberrations: translocation (t)- material from one chromosome is transferred to another, non-homologous chromosome. duplication (dup)- segment of a chromosome is duplicated. deletion (del)- segment a chromosome is deleted.
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2. Chromosome Painting (figure 6.9) Genomic instability in cancer cells II. Diagnosis of chromosomal abnormalities A. Adults: make a Karyotype using cells from one of the following sources: White blood cells (leukocytes) Skin cells (fibroblasts) Tumor cells (biopsy) B. Prenatal Diagnosis 1. Amniocentesis (figure 6.10) - 16 th week of pregnancy Removal and analysis of a sample of ammiotic fluid Contains fetal cells -risk of infection to the mother and a very small risk (<1%) of spontaneous abortion. used when: Older women >35 Parent Carrier of a translocation Previous affected child Parent has a balanced chromosomal rearrangement X-linked disorder Mother might be carrier 2. Chorionic Villus Sampling (CVS) (figure 6.11). - 8-10 weeks of pregnancy Removal of fetal tissue from a region of the placenta called chorionic villus - risks: Less accurate than amniocentesis: chromosomal mosaicism: on rare occasions, the fetus and the chorionic villi have different chromosomal makeups Can cause fatal limb defects (1/1000-1/3000 tests) faster results but with a greater risk of spontaneous abortion . 3. Use of fetal cells from mother's blood
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This note was uploaded on 04/09/2008 for the course BME 80H taught by Professor Rothwell during the Winter '07 term at UCSC.

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Lecture 8 - Lecture #8- Cytogenetics, Chromosomal...

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