Composition of Eukaryotic Genomes
- Highly repetitive DNA (app. 10%)
- satellite DNA
- composed of 10 bp or less repeats (hamster's is CCCTAA)
- 100's of Kb long
- 106 copies/genome
- most of the heterochromatin around the centromere
- minisatellite's
- composed of 15-100 bp repeats
- 1-5 Kb long
- many different ones (unlike the satellite DNA)
- scattered throughout the genome
- telomere's
- a short repeat unit (normally 6 bp -TTAGGG in humans)
- 250-1,000 repeats at the end of each chromosome
- produced enzymatically (telomerase)
- satellite DNA
- Moderatly repetitive DNA
- Nonfunctional
- short interspersed elements (SINEs) in humans
- Alu is an example
- 200-300 bp long
- 100,000's of copies (300,000 Alu)
- scattered locations (not in tandem repeats)
- long interspersed elements (LINEs)
- copia in Drosophila is an example
- 1-5 kb long
- 10-10,000 copies / genome
- pseudogenes (no introns)
- short interspersed elements (SINEs) in humans
- Funtional
- tandem gene family arrays
- 250 copies of rRNA genes
- tRNA genes (50 sites with 10-100 copies ea. in humans)
- histone genes in many species
- dispersed gene families
- actin, globin, immunoglobin, etc.
- tandem gene family arrays
- Nonfunctional
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This document is maintained by: Jeff Bell
Last Update: Wednesday, August 12, 1998