Chromatin Structure

Front 1

epigenetics, def

Back 1

heritable changes in gene expression due to changes other than in the DNA sequence (ex. DNA methylation, histone deacetylation)

Front 2

Understand basic chromosome structure and how DNA is packaged into chromosomes

Back 2

DNA strand > nucleosome > condensed nucleosomes > extended chromatin > condensed chromatin > mitotic chromatid IMAGE

Front 3

Understand higher-order packing and the role histones play in the packaging of DNA into chromosomes

Back 3

xxx IMAGE

Front 4

Understand chromatin transcription

Back 4

xxx

Front 5

Understand what is meant by the "Histone Code"

Back 5

Modifications such as acetylation, methylation, and phosphorylation of histones contributes to epigenetic regulation. Different combinations of A M P can lead to gene silencing vs. expression.

Front 6

What are the 3 ways to convert euchromatin to heterochromatin?

Back 6

deacetylation of histones, addition of H1, increase salt concentration to stabilize electrostatic interactions

Front 7

Where is DNA methylated?

Back 7

5' of deoxycytidine

Front 8

Describe the movement of chromatin within the nucleus.

Back 8

Interconverts between euchromatin and heterochromatin quickly, but whole chromosomes do not move much. Specific genes are associated with specific nuclear compartments.

Front 9

CLINICAL APPLICATION: give an overview of how FISH is used in clinical medicine. Acronym?

Back 9

Fluorescence in situ hybridization. Labeled DNA probe complementary to gene of interest is hybridized to the gene, fluorescently labeling it.

Front 10

What is the approximate length (in base pairs) of a segment of DNA wound around a histone?

Back 10

approximately 146 bp.

Front 11

What force keeps histones bound to DNA?

Back 11

Electrostatic interactions between positively charged histone tails and negatively charged DNA.

Front 12

Give an overview of the structure of histones.

Back 12

(2 x H3-H4 trimer) + (1 x H2A-H2B dimer) = octamer

Front 13

Name the 4 polypeptides that are the "core histone" building blocks of histones. What is their general structure?

Back 13

H3, H4, H2A, and H2B. General structure is 1 long hydrophobic alpha-helix + 2 short hydrophobic alpha-helices

Front 14

How does histone acetylation affect chromatin structure?

Back 14

acetylation of lysine residues by AcCoA neutralizes the positive charge of the histone N-terminus "tails", which decreases the affinity of histones for DNA.

Front 15

Give an overview of histone interactions with DNA.

Back 15

Each histone dimer has 6 DNA binding surfaces that form a DNA ramp.

Front 16

chromatosome, def

Back 16

histone octamer + H1 + 2 full turns of DNA

Front 17

general characteristics of histones?

Back 17

structure and acetylation pattern are highly conserved.

Front 18

Name the modifications of histones that can occur at each of the following amino acid residues: lysine, arginine, serine, threonine.

Back 18

AM M P. lysine (acetylation, methylation), arginine (asymmetric or symmetric methylation), both serine and threonine (phosphorylation)

Front 19

What is the effect of histone modification on gel electrophoresis of histones?

Back 19

histones can take on multiple charges depending on modifications

Front 20

HDAC vs. HAT, acroynm

Back 20

Histone Deacetylase, Histone Acetyl Transferase

Front 21

At what phase in the cell cyle is HDAC active?

Back 21

Function of HDAC is to allow DNA replication, so it is active at the restriction point just before S-phase

Front 22

When does chromatin remodeling occur?

Back 22

When chromatin is decondensed during replication.