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How does differential gene expression occur?
each stage is a potential control point for gene expression and ultimately protein function therefore genes will be deactivated to result in differential gene expression
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What is a chromatin
a complex of DNA and protein, and is found in the nucleus of eukaryotic cells
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What are histones?
- proteins that are responsible for the first level of DNA packing in chromatin
- DNA winds around histones
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What is a euchromatin?
loosely packed chromatin
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During interphase a few regions of chromatin (centromeres and telomeres) are highly condensed into
heterochromatin
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____________ are subject to modification that plays a direct role in regulating the expression of genes
histone tails
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What happens in histone acetylation
acetyl groups are attached to positively charged lysines in histone tails
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What process loosens chromatin structure and thereby promotes the initiation of transcription?
histone acetylation
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What is epigenetics?
modifications to DNA that turn genes "on" or "off." These modifications do not change the DNA sequence, but instead, they affect how cells "read" genes.
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A drug that inhibits the removal of acetyl groups from histone tails would:
generally increase transcription
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In a gene, upstream from the promoter there are:
control elements
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If the control elements are close to the promoter, they are:
proximal control elements
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If the control elements are far from the promoter, they are:
distal control elements
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To initiate transcription, eukaryotic RNA polymerase requires the assistance of proteins called
transcription factors
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In eukaryotes, high level of transcription of particular genes depend on:
control elements interacting with specific transcription factors
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What is an activator?
a protein that binds to an enhancer and stimulates transcription of a gene
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Activators have two functional domains:
one that binds DNA and a second that activates transport
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What do bound activators facilitate and result in?
a sequence of protein-protein interactions that result in transcription of a given gene
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What do repressors do?
block a gene
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Muscle cells differ from nerve cells because the cells:
express different genes
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What are the steps to forming an active transcription initiation complex?
- 1.) Activator proteins bind to enhancer
- 2.) DNA-bending protein binds and transcription factors bind to promoter
- 3.) Formation of active transcription initiation complex
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What is alternative RNA splicing?
a regulated process during gene expression that results in a single gene coding for multiple proteins.
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Describe mRNA degradation: (steps)
- initiated by shortening of the poly-A tail
- removal of 5' cap
- nuclease enzymes chew up mRNA
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What can block the initiation of transcription? How?
regulatory proteins and they bind to 5' UTR which prevents attachment of ribosomes
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What are proteasomes?
giant protein complexes that bind to protein molecules and degrade them
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What enables activators to contact proteins at the promoter, initiating transcription?
The bending of the DNA
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