Lecture 8 Flashcards
(29 cards)
how does DNA become further packed?
Linker histone H1 changes the path the DNA takes as it exits the nucleosome core, forming loops
30 nm fibers is the second level of ____ organization
DNA
looped domains in interphase chromosomes are the third level of ______ organization
DNA
true/false: in level 3 of DNA organization, chromatin fiber is converted into chromatin loops
true
in the forming of chromatin loops, __________ associates with other proteins to form the
SMC ring complex
Structural maintenance of chromosome (SMC) proteins
SMC complex uses energy from _____ hydrolysis to
push out a loop of DNA, similar to an inchworm
ATP
______, a non-histone chromosomal protein, is
part of the SMC ring complex that organizes
interphase chromosomes
Cohesin
chromatin loops are pushed out until they meet which kind of protein?
sequence-specific clamp protein (Size of chromatin loops is regulated by
sequence specific proteins)
In addition to organizing chromosomes, _______
play a role in holding sister chromatids together in
duplicated chromosomes
cohesins
loops within loops (mitotic chromosomes) are the fourth level of _____ organization
DNA
The second set of SMC ring
proteins, _______, replaces
cohesins during mitosis
condensins
condensim, Use energy from _______ to form loops within loops
ATP hydrolysis
true/false: DNA packaging is dynamic
true
which two protein complexes help us gain access to DNA when its condensed?
Chromatin-remodeling complexes
Histone-modifying enzymes
when performing transcription, how do we gain access to the DNA of condensed chromosomes?
by changing the nucleosome
structure at specific regions and specific times
__________: locally changes the position of the DNA
wrapped around nucleosomes, Uses the energy of ATP hydrolysis, Interacts with both the histone octamer and the DNA, Changes the accessibility of DNA to other proteins
chromatin remodelling complex
do chromatin remodelling complexes remain active during mitosis?
NO! Mitotic chromosomes need to be tightly packed
_______: Catalyzes the modification of histones by
adding acetyl, phosphate, or methyl groups
Histone modifying enzymes
what is the consequence to altering the charges of the histone tail?
Loosening of the chromatin structure, the negatively charged DNA and positively charged histone aren’t as attracted to one another electrostatically, loosening the wrapping of DNA
true/false: Interphase chromatin is uniformly packed
false, it is
Regions of DNA with high activity of gene expression – _______ chromatin
extended
Regions where genes are shut down –_________ chromatin
condensed
________: condensed version, constituting about 40% of an interphase chromosome,
Some regions are permanently condensed (centromere or telomeric ends),
Some regions activity has been silenced
heterochromatin
______: open chromatin,
Some regions are more condensed (less gene expression) than others
euchromatin
