Bio 99 Quiz Answers #2 Updated 2026

Bio 99 Quiz Answers #2 Updated 2026

Chromatin is composed of - Answers DNA and protein st st st st st st st st




Each nucleotide contains - Answers a histone octamer composed of 2 copies of each of the
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following proteins: H2A, H2B, H3, and H4
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What is true about histone tails? - Answers - They protrude between the two DNA strands that
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supercoil around the nucleosome.
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- They are the target of numerous chemical modifications
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st - They experience changes in net change, shape, and other properties of histones in response to
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st modification.

- They are recognized by acetylases and metheylases.
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How can repositioning nucleosomes affect transcription? - Answers - Moving nucleosomes could
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cover a promoter resulting in repression of transcription.
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- Moving nucleosomes could expose a promoter resulting in activation of transcription.
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What are characteristics of the transcriptional ground state in higher eukaryotes? - Answers - Gene
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promoters are essentially inactive in the absence of regulatory proteins.
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- Access to promoters is restricted by the structure of chromatin.
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- Virtually every gene requires activation.
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Transcriptionally active chromatin tends to - Answers - be devoid of nucleosomes st st st st st st st st st st st




- be deficient in histone H1
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- contain sites hypersensitive to in vitro treatment w/ DNase 1
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, What is involved in gene inactivation by histone modification? - Answers - Modification leads to
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chromatin condensation
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- The RNA polymerase associated with the gene dissociates from DNA when HDACs bind to the
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corepressor
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- Increased methylation of the nucleosomes occur in the vicinity of the gene.
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What gene is least likely to affect the chromatin state in the vicinity of the gene? - Answers
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mediator protein
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Insulators - Answers - are boundary elements that function to prevent the enhancer for one gene
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from activating the promoter of another gene
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- are DNA sequences that can prevent packaging of a gene into heterochromatin
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- require the zinc-finger protein CTCF to function in higher eukaryotes
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Steroid hormone-nuclear receptor complexes activate transcription by binding to - Answers
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hormone response elements
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A housekeeping gene is one that codes for a product that - Answers is expressed at a constitutive
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level
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What is the least likely to be a result of a mutation in the promoter of a gene? - Answers The level
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of expression of that gene remains the same.
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A transcription factor that enhances gene expression is called a - Answers activator
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Which structural motif is not commonly found in the DNA-binding motifs of proteins that act as
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transcriptional regulators? - Answers B-barrel
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