1. DNA ORGANIZATION IN
CHROMOSOME

2. Key vocabulary
 Nucleoid/ nucleosome
 Chromatin
 Scaffold protein
 Histone/ non histone
 Centromere
 Telomere
 Karyotyping

3. Organization
 Highly dependent on the type of org.
 Prokaryotic vs Eukaryotic org.
 Different technique used to visualise.

4. Precise location
Such a compact space. Question arises on how key activities in
protein synthesis can take place within this limited space.

5. Closer view..

6. Chromatin
 Chromosome discovered by W. Waldeyer.
 Euchromatin –Fibers less packed, disperse
appearance occupying most of the nuclear
region.
 Heterochromatin- More dense area, found at
centromeres.

7. Chromosome number.
Diff. org = diff. no.
 Man 23 pairs =Total 46.
 22 pairs of autosomes
 2 sex chromosomes.
 Cht. size shape + pattern,
 Numbered in order of size.
Different cell diff number eg.
Liver cells 92.

8.  Varies among species.
 Unrelated to the size or biological complexity
of an org.
 An asian deer = 3.
 Diploid – 2 of the chromosome in a set.
 Tetraploid – 4 of each chr.
 Octaploid – 8 of each chr.

9. G-bands
 Certain Tx/ staining techniques (Eg. Giemsa)
will allow chromosomes to have striations.
 Large structures containing approx 107 bp
DNA
 chromosomes can be id by cht. banding
pattern- Used for karyotyping –
 Translocations can be id. by comparing to the
original diploid set.

10. Homologous pairs..

11. Homologous contd..
 Notice that the size,
order of bands, and
shape is the same for
both chromosomes.
 Carry the same genes
in the same order.

12. Human chromosomes..

13. Human Karyotype
Sex
chromosomes

14. Chromosomes and genes..
 The dark lines
represent bands.
 Each chromosome,
bears a particular set
of genes, these genes
are arranged in a
specific order.

15. Typical metaphase chromosome
i. Contains a DNA replication origin
 ii. A centromere to attach the DNA to the mitotic
spindle.
 iii. A telomere located at the end.
 DNA needs to be condensed.
 Chromosomes with AT/ GC base pair specific dyes. When
stained.
 Mitotic chromosomes have a banded structure
. ? Methaphase and not other stages?

16. Basic units of a chromosome
 i. DNA (2.2m = Massive folding + coiling)
 ii. Proteins (Histones, scaffold p, polymerase)
 iii.Small amounts of RNA.

17.  Complex between histones + DNA = chromatin.
 Nucleosome = basic structure of chromatin (beaded appearance)
 Scaffold protein = non-histone p. Nucleosome coils aound it.
 Polymerases = enzymes involved with
a)transcription of the gen. information during protein synthesis
b)replication of the DNA prior to the division of chromosomes.

18. Nucleosome..
 Contains 200 bp DNA.
 Subunit of chromatin
composed of short DNA
wrapped around histone
 8 histone molecules =
octamer.
 Nucleosome fibre is tightly
coiled and looped around
non-histone proteins
 Nucleosomes are packed
together = compact.

19. Placement of genes
 Gene = A region of DNA
that controls hereditary
info specifiying the
sequence of a particular
protein.
 Carries biological info
that must be copied and
transmitted to its
progeny.
 Can be as short/long.
 2001: 30,00/40,000
genes.

20.  Color Blindness
 Muscular Dystrophy
 Fragile X syndrome
 Hemophilia