1. Viral genomes contain DNA or RNA and are packaged into capsids through assembly processes. Bacterial chromosomes contain genes and other sequences compacted by looping and supercoiling.
2. Eukaryotic chromosomes vary greatly in size and contain genes and other sequences. Their DNA must be highly compacted to fit in the nucleus.
3. Eukaryotic DNA wraps around histone proteins to form nucleosomes, which further compact to form chromatin fibers and loop domains anchored to the nuclear matrix. Additional compaction occurs during cell division through condensin and cohesin proteins.
12. Terms and concepts to know: Compaction Coiling Supercoiling Gyrase topoisomerase
13. Plates preventing DNA ends from rotating freely Fewer turns More turns Both overwinding and underwinding can induce supercoiling Figure 10.7 These three DNA conformations are topoisomers of each other These two DNA conformations do not occur in living cells
14. Increasing of ‘coiling’ of the double helix in eukaryotes also occur: - DNA replication - transcription, RNA synthesis from a double stranded DNA
15. Figure 10.8 It makes transcription and translation easier, because the chains melt easier. negative supercoiling Does not only lead to a more compacted nucleoid
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18. Has a genome that is more than twice as large as that of Genome size is very various, especially because of the presence of Repetitive DNA
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20. Prevent chromosome sticky ends and shortening Required for proper segregation during mitosis and meiosis Eukaryotic chromosomes contain many origins of replication approximately 100,000 bp apart Figure 10.11
28. Play a role in the organization and compaction of the chromosome Figure 10.13
29. Regular, spiral configuration containing six nucleosomes per turn Irregular configuration where nucleosomes have little face-to-face contact Figure 10.16
53. The number of loops has not changed However, the diameter of each loop is smaller Condesin travels into the nucleus Condesin binds to chromosomes and compacts the radial loops During interphase, condensin is in the cytoplasm The condensation of a metaphase chromosome by condensin Model !
54. ‘ Chromosome territories’ chromosomen nemen een bepaalde ruimte in in de nucleus: Geen spaghetti Chromosome of a chicken Nucleus where each chromosome is colored differently