The student is expected to: 5C describe the roles of DNA, ribonucleic acid (RNA) and environmental factors in cell differentiation; 6C explain the purpose and process of transcription and translation using models of DNA and RNA; 6D recognize that gene

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The student is expected to5C describe the
roles of DNA, ribonucleic acid (RNA) and
environmental factors in cell differentiation6C
explain the purpose and process of transcription
and translation using models of DNA and RNA 6D
recognize that gene expression is a regulated
process6E identify and illustrate changes
inDNA and evaluate the significance ofthese
changes
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KEY CONCEPT Gene expression is carefully
regulated in both prokaryotic and eukaryotic
cells.
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Prokaryotic cells turn genes on and off by
controlling transcription.

• A promotor is a DNA segment that allows a gene to
  be transcribed.
• An operator is a part of DNA that turns a gene
  on or off.
• An operon includes a promoter, an operator, and
  one or more structural genes that code for all
  the proteins needed to do a job.
• Operons are most common in prokaryotes.
• The lac operon was one of the first examples of
  gene regulation to be discovered.
• The lac operon has three genes that code for
  enzymes that break down lactose.

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• The lac operon acts like a switch.

• The lac operon is off when lactose is not
  present.
• The lac operon is on when lactose is present.

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Eukaryotes regulate gene expression at many
points.

• Different sets of genes are expressed in
  different types of cells.
• Transcription is controlled by regulatory DNA
  sequences and protein transcription factors.

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• Transcription is controlled by regulatory DNA
  sequences and protein transcription factors.

• Most eukaryotes have a TATA box promoter.
• Enhancers and silencers speed up or slow down the
  rate of transcription.
• Each gene has a unique combination of regulatory
  sequences.

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• RNA processing is also an important part of gene
  regulation in eukaryotes.

• mRNA processing includes three major steps.

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• mRNA processing includes three major steps.

• Introns are removed and exons are spliced
  together.
• A cap is added.
• A tail is added.

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Environmental factors influence gene expression,
resulting in different cell types.

• Internal factors can affect cell differentiation.
• Uneven distribution of proteins, mRNA, and
  organelles within a cell can affect gene
  expression.
• Surrounding cells can influence one another by
  sending and receiving signal molecules.

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• Factors in an organisms external environment can
  also affect gene expression.
• Too much oxygen in an organisms environment can
  prevent transcription proteins from being made by
  the cells.
• Temperature can influence gene expression.
• Drugs or chemicals in the external environment
  can influence cell differentiation.
• Light can change the way that genes are
  expressed.