Transcript CH 13: Regulation of Gene Expression

Chapter 10
Section 2 Gene Regulation and
Structure
Objectives
• Describe how the lac operon is turned on or off.
• Summarize the role of transcription factors in
regulating eukaryotic gene expression.
• Describe how eukaryotic genes are organized.
• Evaluate three ways that gene alterations can alter
genetic material.
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New Vocabulary
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Lac operon
Repressor protein
Transcription factor
Intron
Exon
Point mutation
Frameshift mutation
Transposon
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Chapter 10
Section 2 Gene Regulation and
Structure
Regulation of Gene Expression
• Both prokaryotic and eukaryotic cells are able to
regulate
_______________
which genes are expressed and which
needs
are not, depending on the cell’s _________.
– If specific proteins are not needed all of the time, it
waste
would be a ___________
of energy for the cell to
continually make them
• Review…
– What did we call the sequence of DNA that signals for
the start of transcription?
promoter site
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Chapter 10
Section 2 Gene Regulation and
Structure
• In prokaryotes, a _______________
repressor
protein may bind
to DNA in order to ________
RNA
block or ___________
prevent
polymerase from binding to the promoter site and
beginning transcription
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Chapter 10
Section 2 Gene Regulation and
Structure
• The three genes on the prokaryotic DNA strand below are
recognizing ________________,
consuming
involved with ______________,
and
______________
down lactose
breaking
• The entire set of bacterial DNA that controls the
consumption of lactose is called the lac
________________
operon
• Recall that lactose is a disaccharide ___________
found
sugar
in milk
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• When you consume dairy products, the lactose
eventually makes its way into your
intestines
_______________,
where prokaryotic bacteria must
break it down
not consuming dairy, the repressor
• When you are _____
protein binds to DNA and the series of gene are
“off”
_________
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• When lactose is present, it binds to the repressor
shape
protein, changing its ____________,
which causes it to
fall
_________
off of the DNA strand
RNA polymerase from
• Now it is no longer blocking ______
binding with the ______________
site, so
promoter
“on”
transcription may occur and the genes are _______
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Chapter 10
Section 2 Gene Regulation and
Structure
• The regulation of gene expression in eukaryotes is
more _____________
than in prokaryotes for several
complex
reasons…
genes
– Eukaryotes have many more ________
than
prokaryotes
• Typical prokaryote = __________
genes
2000
• Humans = ____________
genes
30,000
grouped
– Similar genes in eukaryotes are not ________
together like in prokaryotes…they are often found
on different _______________
chromosomes
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– Additionally, a nuclear _____________
envelope
separates
transcription and translation in eukaryotes, so
there are many more opportunities for gene
regulation
before
• Regulation may occur _______________,
______________,
or ___________
during
after
transcription,…but most often occurs at the
onset
_____________
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Chapter 10
Section 2 Gene Regulation and
Structure
transcription
• Special eukaryotic proteins, called ____________
factors and ____________
activators help to arrange RNA
polymerase on the promoter site properly
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Chapter 10
Section 2 Gene Regulation and
Structure
Intervening DNA in Eukaryotic Genes
• In eukaryotes, many genes are interrupted by
____________
—long segments of nucleotides that
introns
coding
have no __________
information.
“intervene”
– These portions are said to _______________
with
protein synthesis
• The portions of a gene that are translated or
exons
expressed into proteins are called __________
• After a eukaryotic gene is transcribed, the introns in
the resulting mRNA are _______
out by proteins
cut
spliceosomes
called ______________
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Chapter 10
Section 2 Gene Regulation and
Structure
• Spliceosomes also __________
splice
or “stitch” the
remaining __________
together
exons
exons
• The new mRNA containing only __________,
exits
the nucleus
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• This arrangement of exons and introns in genes may
have an evolutionary advantage…
shuffled between
– Sometimes the exons get ___________
different gene segments, allowing several different
_____________
variations of a gene to exist
12 different
– For example, our cells have _____
hemoglobin genes that are all capable of
producing the protein hemoglobin
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Chapter 10
Section 2 Gene Regulation and
Structure
Mutations
• Errors in DNA ______________
replication
or ____________
division
may cause mutations that code for ____________
incorrect
amino acids
• Mutations may…
– have ____
no effect on an organism
– be ____________
harmful
– Be ____________
beneficial
• The two main types of mutations are gene
_______________
rearrangements and gene _________________
alterations
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Chapter 10
Section 2 Gene Regulation and
Structure
Gene Rearrangements
• Gene rearrangements are mutations that move an
entire
__________
gene to a new location on a
chromosome
– This may affect a gene’s expression because it is
exposed to different _____________
regulatory proteins
– It could be comparable to moving to France but
speak
not being able to __________
French
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• Sometimes gene
rearrangements occur when
divide
DNA does not ___________
properly during cell division
• Other gene rearrangements
are the result of
transposons special
______________,
genes that can actually
jump and change
________
positions along a DNA strand
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• Before a transposition, a
gene sequence may read A
B C, but after it may read
ACB
___________
• Transposons are
responsible for the streaked
color pattern seen on
________
Indian corn… their positions
prevent _________
pigment proteins
from being produced, causing
portions of the cob to lack color
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• Scientists think that transposons
may play a significant role in
_________________
and may
evolution
help researchers pinpoint the
cancer
causes of ___________
• They were actually first
discovered by Barbara
McClintock in the 1950s,
_____________
but her work was not recognized
or honored for more than 20
years
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Chapter 10
Section 2 Gene Regulation and
Structure
Gene Alterations
• Gene alterations are mutations that change a portion
single
of a __________
gene
• Two types of gene alterations are…
point
– _______________
mutations
– _______________
frameshift
mutations
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Chapter 10
Section 2 Gene Regulation and
Structure
Point Mutations
• In a point mutation, a single
changes
nucleotide _____________
• So, if a codon reads GGG,
after a point mutation it may
read _______
GGA
• Since several codons code for
the same amino acid,
sometimes point mutations do
_____
not alter the protein being
made…but sometimes they do
Point mutations may
also be called
substitutions
________________
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Chapter 10
Section 2 Gene Regulation and
Structure
Frameshift Mutations
• In a frameshift mutation,
inserted
nucleotides are __________
deleted
or _________________
• Because the genetic code is
read in ___________,
triplets
insertions and deletions
often upset the triplet
grouping
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Chapter 10
Section 2 Gene Regulation and
Structure
• These mutations may cause a gene’s nucleotides to
__________,
causing the _________
shift
wrong three
nucleotide sequences to be read
• Sometimes scientists compare proteins to
sentences…
– Imagine deleting the letter C from the sentence…
THE CAT ATE
THE ATA TE
____________________
• The remaining triplet sequences would be altered
useless
and rendered ________________
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Objective 1
• Describe how the lac operon is turned on or off.
Off = repressor protein binds to DNA at the operator
and blocks RNA polymerase from binding
On = lactose binds to repressor protein, changing
the shape of it and making it fall off the DNA
strand allowing RNA Polymerase to get past
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Objective 2
• Summarize the role of transcription factors in
regulating eukaryotic gene expression.
They help to arrange RNA polymerase correctly
on eukaryotic DNA
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Objective 3
• Describe how eukaryotic genes are organized.
The genes are located on DNA which coils
up into chromosomes…similar genes are often
scattered on different chromosomes
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Objective 4
• Evaluate three ways that gene alterations can alter
genetic material.
Point mutations
Frameshift mutations – insertion or deletions
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