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Lecture 1

BIOL 1090 Lecture Notes - Lecture 1: Solenoid, Organelle, Consensus Sequence

Course Code
BIOL 1090
Andrew Bendall

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BIOL1090 Lecture 1 13 January 2016
DNA and Chromosome Structure
About 146 nucleosomes wrap around histones
Second level of condensation:- more folding or supercoiling/twisting
o The way the 30nm fibre looks has two options
Depends on the method used to visualize it
Solenoid model vs. zig-zag model
Zig-zag is commonly accepted
o DNA wraps about 3 times around each histone, histone 1 protein (H1) attaches to
each histone, histones then coil together to form the solenoid
Third Level of Condensation
Attaching the 30nm fibre in many positions
30nm is the basic structural unit of the metaphase chromosome
Bacterial Chromosomes
Folds and loops in a very similar way to eukaryotic DNA (Fig 9.15)
o Circular chromosome folded chromosome (flower shape) supercoiled,
folded chromosome (telephone wire flower shape)
We have mitochondrial genomes
o Double stranded, circular
Chloroplasts also have a set of genes dedicated to the processes of what goes on in the
Gives evidence to Endosymbiotic Theory
o One cell lived inside another to live in harmony
Smaller cell had advantages (protection, etc.) but couldn’t live outside of
other organism (obligate parasite?) became an “organelle”
Because of this, we still have some circular DNA
One chromosome is one double-stranded helix
Chromosome ends are protected by telomeres (Fig 9.25)
Consensus sequence a repeated sequence found multiple times in the chromosome
o 5’ (1-4)T (0-1)A (1-8)G 3’
o 500-3000 copies
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