1. DNA Organization in Chromosomes
Chapter 12 Lecture
Concepts of Genetics
Tenth Edition
DNA Organization in Chromosomes

2. 12.1 Viral and Bacterial Chromosomes Are Relatively Simple DNA Molecules

3. Figure 12-1 Electron micrographs of (a) phage  and (b) the DNA isolated from it. The chromosome is 17m long. The phages are magnified about five times more than the DNA.
Figure 12.1

4. Table 12-1 The Genetic Material of Representative Viruses and Bacteria

5. Figure 12-2 Electron micrograph of bacteriophage T2, which has had its DNA released by osmotic shock. The chromosome is 52m long.
Figure 12.2

7. Figure 12-3 Electron micrograph of the bacterium Escherichia coli, which has had its DNA released by osmotic shock. The chromosome is 1200m long.
Figure 12.3

9. 12.2 Supercoiling Facilitates Compaction of the DNA of Viral and Bacterial Chromosomes

10. Figure 12-4 Depictions of the transformations leading to the supercoiling of circular DNA. L equals the linking number.
Figure 12.4

11. Figure 12-4a Depictions of the transformations leading to the supercoiling of circular DNA. L equals the linking number.
Figure 12.4a

12. Figure 12-4b Depictions of the transformations leading to the supercoiling of circular DNA. L equals the linking number.
Figure 12.4b

13. Figure 12-4c Depictions of the transformations leading to the supercoiling of circular DNA. L equals the linking number.
Figure 12.4c

14. Figure 12-4d Depictions of the transformations leading to the supercoiling of circular DNA. L equals the linking number.
Figure 12.4d

15. 12.4 DNA Is Organized into Chromatin in Eukaryotes
Chromatin Structure and Nucleosomes

16. DNA Fun Fact
Length of DNA in human cell ~ 2 meters
No. of cells in human body ~1014
So, total length of DNA in
human body ~ 2 x 1014 meters = 2 x 1011 km
Distance from Earth to Sun ~ 1.5 x 108 km
This means that you have enough DNA in your body to stretch back and forth between the
Earth and Sun 1000 times!

17. Table 12-2 Categories and Properties of Histone Proteins

18. Figure 12.8

19. ~200 bp
147 bp
digest linker DNA

21. Figure 12-9 General model of the association of histones and DNA in the nucleosome, illustrating the way in which the chromatin fiber may be coiled into a more condensed structure, ultimately producing a mitotic chromosome.
Figure 12.9

24. 12.4 DNA Is Organized into Chromatin in Eukaryotes
High Resolution Studies of the Nucleosome Core

25. Figure The nucleosome core particle derived from X-ray crystal analysis at 2.8 Å resolution. The double-helical DNA surrounds four pairs of histones.
Figure 12.10

26. 12.4 DNA Is Organized into Chromatin in Eukaryotes
Heterochromatin

27. 12.5 Chromosome Banding Differentiates Regions along the Mitotic Chromosome

28. Figure A human mitotic chromosome preparation processed to demonstrate C-banding. Only the centromeres stain.
Figure 12.11

29. Figure 12-12 G-banded karyotype of a normal human male
Figure G-banded karyotype of a normal human male. Chromosomes were derived from cells in metaphase.
Figure 12.12

30. Figure The regions of the human X chromosome distinguished by its banding pattern. The designations on the right identify specific bands.
Figure 12.13

31. 12.6 Eukaryotic Chromosomes Demonstrate Complex Sequence Organization Characterized by Repetitive DNA

32. Figure 12-14 An overview of the various categories of repetitive DNA.

33. 12.6 Eukaryotic Chromosomes Demonstrate Complex Sequence Organization Characterized by Repetitive DNA
Satellite DNA

34. Figure Separation of main-band (MB) and satellite (S) DNA from the mouse by using ultracentrifugation in a CsCl gradient.
Figure 12.15

35. Figure In situ hybridization between a radioactive probe representing mouse satellite DNA and mitotic chromosomes. The grains in the autoradiograph localize the chromosome regions (the centromeres) containing satellite DNA sequences.
Figure 12.16

36. 12.6 Eukaryotic Chromosomes Demonstrate Complex Sequence Organization Characterized by Repetitive DNA
Centromeric DNA Sequences

37. Centromeric DNA Sequences
“point” versus “regional” centromeres

38. Figure Nucleotide sequence information derived from DNA of the three major centromere regions of yeast chromosomes 3, 4, 6, and 11.

39. 12.6 Eukaryotic Chromosomes Demonstrate Complex Sequence Organization Characterized by Repetitive DNA
Telomeric DNA Sequences
Middle Repetitive Sequences: VNTRs and STRs
Repetitive Transposed Sequences: SINEs and LINEs
Middle Repetitive Multiple-Copy Genes

40. 12.7 The Vast Majority of a Eukaryotic Genome Does Not Encode Functional Genes
“C- value paradox”