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Gene Expression

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Gene Expression Vocabulary Objectives: Explain how genes expression is controlled in prokaryotes. 2. Explain how gene expression is controlled in eukaryotes. – PowerPoint PPT presentation

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Title: Gene Expression


1
Gene Expression
Vocabulary
  • Objectives
  • Explain how genes expression is controlled in
    prokaryotes.
  • 2. Explain how gene expression is controlled in
    eukaryotes.
  • Gene expression
  • Cellular differentiation
  • Stem cell
  • Pluripotent Multipotent
  • Epigenetics
  • Methylation
  • Histone Modification
  • Lac Operon
  • Promoter
  • Operator
  • Repressor
  • Transcription factors

2
Consider the following
  • Do all of the cells in your body carry out the
    same processes?
  • Do all of the cells in your body make the same
    proteins?
  • Do all of the cells in your body contain the same
    genes?
  • What is the connection between genes and protein
    production?
  • How is it possible for different types of cells
    to exist in your body?

3
Gene Expression
  • All somatic cells contain a complete set of
    chromosomes
  • Not all genes get transcribed and translated.
  • Example
  • Skin cells will not translate genes to make
    hemoglobin, or insulin.

4
Cell Differentiation
  • Differentiation is when cells become specialized
    in structure and function
  • It results from selective gene expression, the
    turning on and off of specific genes.

5
Stem cells
  • Pluripotent (can become any type of cells) or
    multipotent (many types of cells)
  • Stem cell research
  • Potential to help cure/treat conditions involving
    damaged cells (replace cells of damaged spinal
    cords, or cardiac muscles, etc.)

Tutorial on stem cells http//www.stemcellresea
rch.umich.edu/overview/tutorial.html
6
Stem cells Therapeutic Cloning
  • Use embryonic stem cells to create specialized
    human cells.
  • Goal Cure disease
  • Embryo does not develop into a human.

Allowed in U.S. (state by state) w/ restrictions
7
Why do people bank cord blood? http//www.theceleb
worth.com/top-10-cord-blood-banks/
  • Sources of Stem Cells
  • Embryonic cells (after fertilization to a few
    weeks)
  • Placenta Umbilical cord blood
  • Bone marrow in adults

8
What Controls Which Genes Get Translated
(Expressed)?
  • Prokaryotes (bacteria)

Eukaryotes
  • Operon System
  • Promoter and Operator sequence before genes
  • Switch on/off genes

Transcription factors
9
Prokaryotes Gene Expression
Operon Promoter Operator Genes Promoter
where RNA polymerase binds. Operator Where
repressor protein binds.
Operon Off Repressor protein binds to operator
when lactase is not needed. Stops transcription
of genes. Operon On Lactose present ? binds to
repressor protein. Repressor released, genes
transcribed.
10
Gene Expression in Prokaryotes The Lac Operon
Animation
11
Prokaryotes lac operon system
Operon sequence of instructions for turning
on/off transcription. Located before gene
sequences. Includes promoter and operator
sequences. Promoter RNA polymerase binds to
starting line for transcription. Operator
site where Repressor protein binds and STOPS
TRANSCRIPTION (when proteins are not needed)
12
lac operon system
Repressor protein binds to operator site ?
prevents transcription Repressor proteins
alternate shape! Lactose present binds to
repressor protein changes repressor shape
repressor DOES NOT fit on operator site genes
transcribed proteins for lactose digestion made.
Lactose not present repressor shape allows it
to bind to operator and STOP transcription
(proteins not needed).
13
Animation of lac operon system http//www.sumanasi
nc.com/webcontent/animations/content/lacoperon.htm
l McGraw Hill animation of lac operon http//highe
red.mcgraw-hill.com/sites/dl/free/0072835125/12699
7/animation27.html
Eukaryotic Gene Expression Transcription Factors
  • More complex than prokaryotes

14
Eukaryotes Gene Expression
  • Proteins called transcription factors regulate
    transcription by binding to promoters or RNA
    polymerase
  • Turned ON or OFF by chemical signals in the cell
  • More elaborate (than prokaryotes)
  • Genes are not controlled in clusters

15
Eukaryotes Gene Expression
16
Epigentics Gene Expression
Epigenetics Environmental factors (chemicals or
temperatures) can activate or deactivate genes
and influence the expression of those genes in
future generations. http//theweek.com/article/ind
ex/238907/epigenetics-how-our-experiences-affect-o
ur-offspring
17
The Agouti Mice
http//www.pbs.org/wgbh/nova/body/epigenetic-mice.
html
18
Epigenetics
  • Heritable traits that do not involve changes in
    the underlying DNA sequence (in addition to
    changes to the genetic sequence)
  • Used to describe any aspect other than DNA
    sequence that influences the development of an
    organism.
  • Involves chemical modifications that mark
    certain genes with a distinct signature
    biological punctuation
  • ex) Doctors v. Doctors

NOVA clip (14min)
19
DNA Packing Helps Regulate Eukaryotic Gene
Expression
  • A single chromosome contains app. 4cm of DNA
  • Coiling and folding enables all this DNA to fit
    in the nucleus
  • This packing prevents gene expression by blocking
    transcription (protein contact with DNA)
  • Some regions of interphase chromosomes
    (chromatin) are highly packed like mitotic
    chromosomes
  • The genes in these packed regions are generally
    not expressed

20
How are genes turned on or off? 1. Methylation
Methyl groups added to DNA turn off
transcription. 2. Histone modification Proteins
bind to histones (proteins that DNA is wrapped
around) and causes histones to tighten DNA
coiling ? turn off transcription
What causes methylation or histone
modification????
21
(No Transcript)
22
Gene Expression X chromosome Inactivation
  • Female mammals inherit 2 X chromosomes, but do
    not make twice as much X-coded proteins
  • One X in each somatic cell condenses into a
    compacted, inactive Barr body.
  • The same X is not turned off in every cell

23
X Inactivation Cat Fur - Tortoiseshell
24
X Inactivation Cat Fur - Calico
25
Turning Eukaryotic Genes On Off
  • Eukaryotic RNA polymerase needs assistant
    transcription factor proteins
  • Activator proteins bind to enhancers (not
    adjacent to the gene)
  • DNA bends interacts with other transcription
    factors, facilitating correct RNA polymerase
    attachment

Gene Switches
26
Alternative RNA Splicing
  • More than one type of polypeptide can result from
    a single gene
  • Different exons are spliced together as a result
    of alternative splicing

27
Homeotic Genes
  • Master control genes that regulate the genes that
    actually control the anatomy of body parts
  • Discovered by studying bizarre fruit fly
    mutations
  • Mutation in a single gene led to legs growing out
    of head in place of antennae

28
Epigenetics NOVA introduction 13 minutes
http//www.pbs.org/wgbh/nova/body/epigenetics.html
Agouti mice video http//www.pbs.org/wgbh/nova/b
ody/epigenetic-mice.html Gene switches (PBS)
slide show http//www.pbs.org/wgbh/nova/body/gene-
switches.html Ghost in Your Genes
(PBS) https//www.youtube.com/watch?v8oUJQkUk6P8
Epigenome at a Glance http//learn.genetics.utah.
edu/content/epigenetics/ Articles for
Epigentics http//discovermagazine.com/2013/may/13
-grandmas-experiences-leave-epigenetic-mark-on-you
r-genes http//theweek.com/article/index/238907/e
pigenetics-how-our-experiences-affect-our-offsprin
g
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