1. Genome structures

3. C-value paradox: no correlation between complexity of an organism and genome size.
Table 7.2 Genomes 3 (© Garland Science 2007)

4. Genome of Fritillaria ≈ 40 times larger than human genome.

6. There is an increase in the number of introns and of repeat sequences going from bacteria to “lower” and “higher” eukaryotes.

7. Schematic of RNA splicing in eukaryotes.

9. A processed pseudogene
Figure Genomes 3 (© Garland Science 2007)

10. Figure 7.21 Genomes 3 (© Garland Science 2007)

11. There is an increase in the number of introns and of repeat sequences going from bacteria to “lower” and “higher” eukaryotes.

12. Repetitive DNA in genomes
Mostly DNA and RNA
transposons
Repetitive DNA
Tandemly repeated DNA is in the centromere (satellite DNA), the telomeres (minisatellites), and microsatellites.
Genome-wide repeats: Retroelements (LTRs, LINEs, SINEs) and DNA transposons. Make up about 46% of the human genome.
Tandem repeat means that the same sequence is repeated many times in the same position. The length of the repeated sequence can be one to a few base pairs (as in microsatellites) up two more than 100 bp (as in satellite DNA in centromeres). Tandem repeats are not genome-wide repeats because they do not occur in other places of the genome.
Satellite DNA
(micro-, mini-, satellites)

13. Microsatellite analysis (24 samples)
Microsatellites on the short arm of human chromosome 6 amplified by PCR. Blue or green marker. Red bands are size markers. 24 samples. Apparently 12 different microsatellites amplified by PCR.
In US 13 microsatellites are used for this type of genetic profiling, in the UK 10.
Figure Genomes 3 (© Garland Science 2007)

14. Chromatin organization

15. Bacterial chromosomes are generally negatively
supercoiled and associated with a number of proteins,
primarily HU proteins

16. Eukaryotic nuclear chromosomes are negatively
supercoiled by association with histone proteins

17. Origin of replication General features of eukaryotic chromosomes
Only 1 origin of replication in bacterial genomes. Eukaryotes have multiple origins of replication, about 1 every to bp.

18. Centromeres are necessary for correct segregation of
chromosomes to daughter cells in cell division
Centromeres associate with proteins to form kinetochores,
i.e. attachment sites for microtubules

19. Centromeres vary in size. Most consist of tandem repeats.

20. Origin of replication General features of eukaryotic chromosomes
Only 1 origin of replication in bacterial genomes. Eukaryotes have multiple origins of replication, about 1 every to bp.

21. Telomeres consist of tandemly repeated DNA
(minisatellites) at the ends of chromosomes.
They maintain the ends of linear chromosomes.
5’-TTAGGG-3’ is the repeat unit in humans.

22. Chromatin organization is not fixed
Cell cycle

23. Chromatin organization is not fixed

24. Chromatin organization is not fixed
Cohesin- and condensin protein
complexes induce formation of
M phase chromosomes.

25. Chromatin organization is not fixed

26. Proteolysis of cohesins allows segregation of sister chromatids.
Condensins
Cohesins
Proteolysis of condensins
leads to interphase
chromosomes.

27. Mitosis
Meiosis

28. Chromatin organization is not fixed
Interphase
M-phase

29. General organization of interphase
chromatin in the nucleus

30. Nucleosomes

31. Histones are the core proteins of nucleosomes

32. Histones are the core
proteins of nucleosomes

33. Histones are the core proteins of nucleosomes

34. Histones are the core
proteins of nucleosomes

35. Assembly of nucleosomes is promoted by histone chaperones
Proliferating cell nuclear antigen
(PCNA) = sliding clamp

36. Assembly of nucleosomes is promoted by histone
chaperones

37. Histone H1 is a
linker histone

38. Structural changes in nucleosome positioning
in the presence of linker histone H1
+ H1
no H1

39. General organization of interphase
chromatin in the nucleus

40. Possible organization of the 30 nm fiber

41. Histone core modifications:
CENP-A can replace histone H3 in centromeres.
H2A and H2B variants are also found in histone cores.

42. General organization of interphase chromatin in the nucleus
Euchromatin, heterochromatin

43. Histone tail modifications
influence chromatin structure

44. Histone modifying protein complexes

45. Histone tail modifications alter chromatin structure

47. Histone tail modifications cause changes
in chromatin structure
loose
tight

48. Histone tail modifications create binding
sites for protein complexes that alter
the structure of chromatin

49. Nucleosome remodeling complexes alter the
position of nucleosomes

50. Nucleosome remodeling complexes alter the
position of nucleosomes

51. DNA methylation alters chromatin structure

52. Genomic imprinting