Fishing for Chromosomes Ankur Shah

Chromosome Structure 23 pairs of chromosomes (22 autosomes) p and q arms; centromere and telomere Normal karyotypes: 46,XX and 46,XY Prophase & metaphase chromosomes consist of 2 identical sister chromatids (held together by the centromere) Each germ cell contains only 23 chromosomes (1 member of each pair)

Introduction to Karyotypes A karyotype is a picture of an organism's genetic make-up in which the chromosomes of a cell have been stained so that the banding pattern of the chromosomes appear. Cells in Metaphase are stained to show distinct parts of the chromosomes The cells are then photographed through a microscope and enlarged The chromosomes are cut from the photograph and arranged according to size, shape, centromere position, and banding patterns.

A Sample Cell during Metaphase

Normal Male Karyotype (46,XY)

Chromosome groups: A - G

Chromosome Abnormalities - Aneuploidy: N = 23 chromosomes Euploidy: Diploid (2n) Triploid (3n) Tetraploid (4n) Aneuploidy A chromosome number that’s not an exact multiple of n (23 chromosomes) Due to meiotic non-dysjunction E.g. Trisomy (T13, 18, 21); Monosomy (Turner syndrome)

Aneuploidy - Trisomy 13

Aneuploidy - Trisomy 18

Triploid Karyotype (69, XXY)

What is FISH? Fluorescent In Situ Hybridization

Why Use Fish? Fast Can utilize Interphase Cells Translocations Deletions Rearrangements Makes Karyotyping much easier

The Downside of Fishing Requires large number of cells (200-300) Expensive! Can only search for one defect at a time

Examples of Fish

More Examples of Fish

Just a few more

Hey that isnt Fish! THE END