| Abstract Detail
Application of FISH in Support of Sequencing Plant Genomes - Afternoon Stack, Steve [1]. Chromosome Structure and FISH. IN the tomato sequencing project, we are using FISH to determine the positions of DNA segments (in BACs) on chromosomes. Because of this, understanding the structure of chromosomes is of paramount importance in interpreting the location of BACs relative to one another. The underlying basis of all eukaryotic chromosomes is a single DNA double helix in each chromatid. In a metaphase chromosome, the DNA is packed efficiently into nucleosomes that are folded into a 30 nm fiber that is looped on a protein scaffold to form a chromonema that is coiled to form the arms of a chromatid. This arrangement is so compact that a 2.5 cm long segment of DNA from a single tomato chromatid is folded into a chromosome that is only 2.5 μm long, a 10,000:1 folding ratio. Thus, resolution of FISH is 10,000-fold better when done on naked DNA (fiber FISH), than when it is done on metaphase chromosomes. For three reasons, pachytene chromosomes are generally superior to metaphase chromosomes use in FISH: (1) Pachytene chromosomes are 10X longer than metaphase chromosomes so resolution is 10X better than on pachytene chromosomes. (2) Pericentric heterochromatin can be distinguished from euchromatin so the sequencing effort can be concentrated in gene-rich euchromatin. And (3) homologous chromosomes are synapsed in pachytene chromosomes, so there are four closely associated copies of each DNA sequence to use as a FISH target compared to only two DNA segments in a metaphase chromosome. For these reasons, FISH in the tomato sequencing project is being performed primarily on pachytene chromosomes.
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1 - Colorado State University, Biology, Fort Collins, CO, 80523-1878, USA
Keywords:
fiber FISH
pachytene chromosomes
chromosome structure
fluorescence in situ hybridization
FISH.
Session: SAT06-1
Location: Hall of Ideas Room G/Monona Terrace
Date: Wednesday, July 26th, 2006
Time: 2:00 PM
Abstract ID:439 |
