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Cell Bio > Lecture 8 > Flashcards

Lecture 8 Flashcards

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Biology 101 flashcards
1
Q

how does DNA become further packed?

A

Linker histone H1 changes the path the DNA takes as it exits the nucleosome core, forming loops

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2
Q

30 nm fibers is the second level of ____ organization

A

DNA

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3
Q

looped domains in interphase chromosomes are the third level of ______ organization

A

DNA

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4
Q

true/false: in level 3 of DNA organization, chromatin fiber is converted into chromatin loops

A

true

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5
Q

in the forming of chromatin loops, __________ associates with other proteins to form the
SMC ring complex

A

Structural maintenance of chromosome (SMC) proteins

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6
Q

SMC complex uses energy from _____ hydrolysis to
push out a loop of DNA, similar to an inchworm

A

ATP

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7
Q

______, a non-histone chromosomal protein, is
part of the SMC ring complex that organizes
interphase chromosomes

A

Cohesin

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8
Q

chromatin loops are pushed out until they meet which kind of protein?

A

sequence-specific clamp protein (Size of chromatin loops is regulated by
sequence specific proteins)

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9
Q

In addition to organizing chromosomes, _______
play a role in holding sister chromatids together in
duplicated chromosomes

A

cohesins

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10
Q

loops within loops (mitotic chromosomes) are the fourth level of _____ organization

A

DNA

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11
Q

The second set of SMC ring
proteins, _______, replaces
cohesins during mitosis

A

condensins

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12
Q

condensim, Use energy from _______ to form loops within loops

A

ATP hydrolysis

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13
Q

true/false: DNA packaging is dynamic

A

true

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14
Q

which two protein complexes help us gain access to DNA when its condensed?

A

Chromatin-remodeling complexes
Histone-modifying enzymes

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15
Q

when performing transcription, how do we gain access to the DNA of condensed chromosomes?

A

by changing the nucleosome
structure at specific regions and specific times

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16
Q

__________: 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

A

chromatin remodelling complex

17
Q

do chromatin remodelling complexes remain active during mitosis?

A

NO! Mitotic chromosomes need to be tightly packed

18
Q

_______: Catalyzes the modification of histones by
adding acetyl, phosphate, or methyl groups

A

Histone modifying enzymes

19
Q

what is the consequence to altering the charges of the histone tail?

A

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

20
Q

true/false: Interphase chromatin is uniformly packed

A

false, it is

21
Q

Regions of DNA with high activity of gene expression – _______ chromatin

A

extended

22
Q

Regions where genes are shut down –_________ chromatin

A

condensed

23
Q

________: condensed version, constituting about 40% of an interphase chromosome,
Some regions are permanently condensed (centromere or telomeric ends),
Some regions activity has been silenced

A

heterochromatin

24
Q

______: open chromatin,
Some regions are more condensed (less gene expression) than others

A

euchromatin

25
Q

true/false: The structure of chromatin varies along a single interphase chromosome

A

true

26
Q

true/false: Heterochromatin spreads to neighboring regions
of DNA

A

true!

27
Q

how does heterochromatin spread to neighboring regions
of DNA?

A

Histone tail modifications attract a set of heterochromatin-specific proteins, including
histone-modifying enzymes.
This extends the region of heterochromatin until
it encounters a barrier DNA sequence.

28
Q

how do we stop the spreading of heterochromatin?

A

A barrier DNA sequence stops the propagation

29
Q

____________: Randomly, one of the two X chromosomes
becomes highly condensed into heterochromatin early in embryonic development

A

X chromosome inactivation, Barr bodies

Cell Bio (11 decks)

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