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BIOL 308 Lecture 7 What is a nucleoprotein?
Specific protein that assists in the wrapping and tight packaging of linear DNA molecules TERM 2
Long thin strands of nucleoprotein -->
chromatin -->
DEFINITION 2 Get organized into chromatin fibers which are further condensed and called CHROMOSOMES! TERM 3
How is chromatin organized? What is the
fundamental unit of organization?
DEFINITION 3 -Chromatin is organized like beads on a string-nucleosome TERM 4
What does each nucleoside contain?
DEFINITION 4 -octet of histones which is wrapped by DNA TERM 5
Two important aspects of chromatin
organization?
DEFINITION 5 HISTONES package DNATopoisomerase aid in chromatin organization b/c it is important for supercoiing
What do loops of chromatin fibers attach
to?
Scaffold proteins --> frames around which things are built TERM 7
More organization
DEFINITION 7 10 nm nucleosome fiber condenses into 30 nm diameter fiber who is in it's predominant form at the interphase nucleus TERM 8
Euchromatin vs. Heterochromatin
DEFINITION 8 Euchromatin consists of transcriptionally active DNA (susceptible to DNAse activity)Heterochromatin consists of transcriptionally inactive DNA that is less susceptible to DNase TERM 9
What is constitutive heterochromatin? Where
is it found?
DEFINITION 9 -highly condensed inactive chromatin consisting if highly repeating DNA sequences-found in centromeres and telomeres TERM 10
What is facultative
heterochromatin?
DEFINITION 10 -not active in any particular tissues-forms under specific circumstances to silence gene expression
T/F: Histone proteins are highly conserved
(same in nearly all organisms)
TRUE - they are vital! TERM 17
Reformation of Nucleosomes
DEFINITION 17 -reformation necessary because DNA replication involves disassembly of nucleosomes-newly replicated DNA immediately packaged, first bind H3 + H4 tetramers, then H2A + H2B dimers and finally H1 is last. TERM 18
What are chaperone proteins? What do they
do?
DEFINITION 18 -negatively charged proteins that assist in histone assembly- they are negatively charged because histones themselves are positively charged (due to several +ve lysines) TERM 19
What is the function of the N-terminal tails of
Histone?
DEFINITION 19 -direct DNA wrapping --> necessary for the formation and stabilization of the 30 nm fiber TERM 20
Mod. of chromatin is necessary for replication
to start. What are the three mods?
DEFINITION 20
- Acetylation of lysine in histone tail --> associated with active gene expression (acetylated form is negative)2)Methylation of histone tail --> associated with active/inactive expression3) Phosphorylation (serine) --> generally associated with active geneModificaitons neutralize parts of the tail
What does acetylation of lysine and
phosphorylation due to the protein?
Reduces the overall positive charge of the protein TERM 22
In the DNase test, what happens if a signal is
produced? What if there is no signal?
DEFINITION 22 Signal - no gene expressionNo signal - gene expression in progress, DNA free of histones for digestion with DNase
