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.
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.