BIOL1006 Lecture Notes - Lecture 2: Kinetochore, Ftsz, Dna Replication

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25 Jun 2016
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Lecture 2
prokaryotic cell division - division by binary fission
genome made of single, circular DNA found in nucleoid area
replication of DNA begins at specific site and goes bidirectionally
around to specific site of termination
cell elongates, DNA gets attached to the membrane
septum - new membrane growing near the midpoint during division
composed of FtsZ protein ring
eukaryotic cells developed mitosis to deal w/ larger, nucleus-enclosed
genomes
mitosis - occurs differently in different organisms
protists - 2 ways
microtubules (w/ tubulin) pass through nucleus membrane tunnels and
sets up axis for division (nucleus remains intact)
microtubule spindle forms between centrioles at opposite sides;
kinetochore microtubules pull chromosomes to each pole (nucleus
remains intact)
yeasts - spindle microtubule forms inside nucleus between poles
single kinetochore microtubule attaches to chromosomes, pulls them
to each end
animals - spindle microtubule forms between centrioles outside the
nucleus
nucleus envelope breaks down
kinetochore microtubules attach chromosomes to poles
chromosome - found in cells of all eukaryotes; 40% DNA, 60%
protein
most eukaryotes have 10-50 chromosomes (humans have 46, 23
pairs)
monosomy - condition where organism lacks a chromosome; won’t
survive embryonic development
trisomy - extra copy of a chromosome; fatal unless extra copy of very
small chromosome (genetic defects still take place)
chromatin - DNA/protein complex
heterochromatin - chromatin domains not expressed
euchromatin - chromatin domains expressed
DNA coiled to allow it to fit in smaller space
nucleosome - 200 nucleotides coiled around 8 histones
solenoid - coils of a string of nucleosomes wrapped together; radially
loops around protein scaffold during mitosis
histones (positively charged) attract negatively charged phosphate
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