人类染色体.ppt

医学课件 Chromose Abnomalities 染色体病 A. What Is a Chromosome? Chromosome -- in the eukaryotic nucleus, one of the threadlike structures consisting of chromatin and carry genetic information arranged in a linear sequence. B. Chromosome Structure Chromosome Staining Structure Metaphase chromosome spread Staining techniques G-banding Staining with the trypsin-giemsa method reveals a series of alternating light and dark bands called G bands. G bands are numbered and provide addresses for the assignment of gene loci. C-banding C-banding stains centromeres. R-banding R-banding is the reverse of c-banding and stains non-centromeric regions in preference to centromeres. Q-banding Q-banding is a fluorescent pattern obtained using quinacrine for staining. The pattern of bands is very similar to that seen in g-banding. What a karyotype Tells Us (1) What a karyotype Tells Us (2) Down syndrome (an extra 21 chromosome) Turner syndrome (females with only one X chromosome) Klinefelter syndrome (males with two X chromosomes and a Y chromosome) Other sex chromosome conditions, such as XXX or XYY Any other aneuploidy, which is an extra or missing single chromosome What a karyotype Tells Us (3) Triploidy, which is an extra set of chromosomes, so there are three of each and 69 total Mosaic chromosome conditions, in which a portion of the cells show an abnormal number or arrangement of chromosomes and a portion show a normal number and arrangement Translocations, which are rearrangements of the chromosome material Large missing or extra pieces of chromosome material that are visible under a microscope What a karyotype Cannot Tell Us What a karyotype Cannot Tell Us (2) What a karyotype Cannot Tell Us (3) Tay-Sachs disease Sickle cell disease Dwarfism Breast cancer Cleft lip/palate Heart defects D. Chromosomal Abnormalities 医学课件 There are many genetic conditions that are the result of single gene mutations. Additionally, there are many genetic conditions that are