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25 Cards in this Set
- Front
- Back
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what makes up the protein component of a nucleosome
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2 tetramers of histone proteins
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what are the 3 significant properties of euchromatin
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uncoiled, active, areas of gene expression
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what are 3 significant properties of heterochromatin
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condensed, inactive, lack genes or contain genes that are repressed
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which replicates earlier, euchromatin or heterochromatin
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euchromatin before heterochromatin during S phase
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what are 2 examples of heterochromatin
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centromere
telomere |
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what is the telomere
what is its purpose |
repeated structures at the end of a chromosome
-aid in structural integrity of the chromosome |
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what are histones, and what are non-histones
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Histone: positively charged protein
Non-Histone: less positively charged protein |
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what does a nucleosome consist of
-how many base pairs |
core of 8 histone proteins
-146 |
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what are the 2 types of tetramers
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2 units of H2A, H2B
2 units of H3, H4 |
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what makes up a histone core
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2 copies of H2A, H2B, H3, H4
H1 resides outside core |
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what is the purpose of H1
-what structure is it associated with |
binds with linker DNA to connect nucleosomes
-"beads on a string" |
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what are the 4 levels of compaction of DNA into chromatin
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1. DNA wraps around nucleosomes (11 nm)
2. Nucleosomes associate together (30 nm) 3. Formation of Looped Domains (300 nm) 4. Condensed further to chromosome (700 nm) |
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what are MARs
-why are they important |
DNA sequences that attach the DNA in looped domains to the nuclear matrix
-they are located near regions that are actively expressed |
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what are nucleosomes grouped together for form 30 nm structures called
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solenoids
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what is relationship between histones and transcription factors
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they compete for DNA
-regions that are nucleosome depleted are where genes are transcribed -regions that contain nucleosomes disallows transcription |
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what is the purpose of the SWI/SNF complex
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it loosens the attachment between histones and DNA, allowing nucleosomes to slide apart
-this allows for RNA polymerase to recognize specific sites and express genes |
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where do histone modifications primarily take place
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on histone tails
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what is the ChIP method used for
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detecting protein footprints
(where proteins bind to DNA) |
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what is histone acetylation associated with
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activating transcription; gene expression
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how does histone acetylase work
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neutralizes positive charge in histones, loosens chromatin packaging
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how does histone deactylase work
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re-establishes positive charge of histones, and represses transcription
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where is histone acetylation of found
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at areas of high gene expression
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where can histone methylation occur
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arginine or lysine residues
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what is histone methylation correlated with
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both gene expression and gene repression
(transcription activation and repression) |
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what is the histone code hypothesis
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modifications of histones function to direct specific and distinct DNA-templated programs
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