Gene%20Regulation%20results%20in%20differential%20Gene%20Expression,%20leading%20to%20cell%20Specialization - PowerPoint PPT Presentation

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Gene%20Regulation%20results%20in%20differential%20Gene%20Expression,%20leading%20to%20cell%20Specialization

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Title: Gene Regulation results in differential Gene Expression, leading to cell Specialization Author: Dawn Koons Last modified by: dkoons Created Date – PowerPoint PPT presentation

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Title: Gene%20Regulation%20results%20in%20differential%20Gene%20Expression,%20leading%20to%20cell%20Specialization


1
Gene Regulation results in differential Gene
Expression, leading to cell Specialization
  • Eukaryotic DNA

2
Epigenetics Ghost in Your Genes
  • Watch to see how your environment and your
    choices influence inheritance
  • http//www.youtube.com/watch?vCiAyLPeCTMUfeature
    sharelistPLA2E1F3FFBFAE1CB6

3
Differential Gene Expression
  • Nucleosome Packing DNA wraps around histone
    proteins to form a structure called a nucleosome.
    Nucleosomes help pack DNA into eukaryotic
    chromosomes.
  • When acetyl groups attach to the histone proteins
    the DNA in chromosomes loosens to allow for
    transcription.
  • The addition of methyl groups to histone proteins
    can cause DNA to condense thus preventing
    transcription.
  • In Genomic Imprinting, methylation regulates
    expression of either the maternal or paternal
    alleles of certain genes at the start of
    development.

4
Organization of Typical Eukaryotic Genes
Fig. 18-8-3
5
The Roles of Transcription Factors
  • Regulatory Proteins, repressors and activators,
    operate similarly to those in prokaryotes,
    influencing how readily RNA polymerase will
    attach to a promoter region. In many cases,
    numerous activators are acting in concert to
    influence transcription.

6
Fig. 18-9-3
Promoter
Activators
Gene
DNA
Distal control element
Enhancer
TATA box
General transcription factors
DNA-bending protein
Group of mediator proteins
RNA polymerase II
RNA polymerase II
Transcription initiation complex
RNA synthesis
7
Coordinately controlled eukaryotic genes
  • A particular combination of control elements can
    activate transcription only when the appropriate
    activator proteins are present.
  • All cells of an organism have all
    chromosomes/genes but certain genes are only
    active in certain cells. The transcription
    factors present in the cell determine which genes
    will be active and which wont (but they are both
    still present)

8
Fig. 18-10
Enhancer
Promoter
Albumin gene
Control elements
Crystallin gene
LENS CELL NUCLEUS
LIVER CELL NUCLEUS
Available activators
Available activators
Albumin gene not expressed
Albumin gene expressed
Crystallin gene not expressed
Crystallin gene expressed
(b) Lens cell
(a) Liver cell
9
Post Transcriptional Regulation
  • Alternate Gene Splicing - different mRNA
    molecules are produced from the same primary
    transcript, depending on which RNA segments are
    treated as exons and which as introns

10
Fig. 18-11
Exons
DNA
Troponin T gene
Primary RNA transcript
RNA splicing
or
mRNA
11
Noncoding RNAs role in gene expression
  • RNA Interference, noncoding RNAs play multiple
    roles in controlling gene expression. MicroRNAs
    (miRNAs) and Small inserting RNAs (siRNAs) are
    small single-stranded RNA molecules that can bind
    to mRNA. These can degrade mRNA or block its
    translation. The difference between the two is
    that they form from different RNA precursors.

12
Fig. 18-13
Hairpin
miRNA
Hydrogen bond
Dicer
miRNA
miRNA- protein complex
3?
5?
(a) Primary miRNA transcript
Translation blocked
mRNA degraded
(b) Generation and function of miRNAs
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