Ch. 10 Notes
DNA: Transcription and
Translation
GOALS
 Compare the structure of RNA with that of DNA
 Summarize the process of transcription
 Relate the role of codons to the sequence of amino
acids that results after translation
 Outline the major steps of translation
 Discuss the evolutionary significance of the genetic
code
 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 point mutations can alter
genetic material
Decoding the Information in
DNA
RNA
1. Nucleic acid made of
nucleotides linked together
2. Single stranded
Decoding the Information in
DNA
RNA
3. Contains 5C ribose sugar
(one more oxygen than
DNA)
Decoding the Information in
DNA
• RNA
• 4. Has A, G and C bases,
but no T
• 5. Thymine replaced by
uracils (which pairs with
adenine)
Decoding the Information in
DNA
Transcription Instructions for making
protein are transferred from
a gene to an RNA molecule
Decoding the Information in
DNA
Translation Two types of RNA are used
to read instructions on RNA
molecule and put amino
acids together to make the
protein
Decoding the Information in
DNA
Gene
Protein synthesis
Expression Protein making process
based on information
encoded in DNA
TRANSCRIPTION
Transcription Transfers info from a gene
on DNA to RNA
In prokaryotes- occurs in
cytoplasm
In eukaryotes- occurs in
nucleus
TRANSCRIPTION
Transcription  1. RNA polymerase binds to start
signal “promoter” on DNA
(STEPS)
 2. RNA polymerase unwinds and
opens DNA double helix
TRANSCRIPTION
Transcription 3. RNA polymerase reads
(STEPS)
genes- adds and links
matching nucleotides by
base pairing (A-U and G-C)
TRANSCRIPTION
Transcription  4. RNA polymerase reaches stop
signal at end of gene
(STEPS)
 5. As RNA polymerase works, a single
strand of RNA grows
TRANSCRIPTION
Transcription 6. DNA helix zips itself back
(STEPS)
up as RNA polymerase
passes by
TRANSCRIPTION
Transcription 7. Many identical RNA
(STEPS)
molecules are made
simultaneously
Feather like appearance in photos
The GENETIC CODE
Messenger mRNA
RNA
Made when cells need a
protein made
Delivers protein making
instructions from gene to
translation site
Instructions written in codons
The GENETIC CODE
Codons
Three nucleotide sequences
along mRNA
64 possible codons
Each corresponds to:
An amino acid OR
A stop signal OR
A start signal
Can You Tell Me?
1. During DNA replication, what molecule
“reads” the strand of DNA to make the
matching strand?
2. During transcription, what molecule “reads”
the DNA?
3. What material does the transcription
process create?
The GENETIC CODE
• RNA’s role
in
translation
• Takes place in cytoplasm
• Transfer RNA (tRNA) and
ribosomes help in protein
synthesis
The GENETIC CODE
Transfer
RNA
tRNA
Single strand, carries amino
acid
Folded shape
Contains anticodon
The GENETIC CODE
Anticodon
3 nucleotides on tRNA that
are complementary to a
mRNA codon
The GENETIC CODE
Ribosomal rRNA makes up part of
RNA
ribosomes
The GENETIC CODE
Translation 1. mRNA leaves nucleus,
process
enters cytoplasm
2. Ribosome hooks onto
mRNA at start codon
The GENETIC CODE
Translation
process
 3. tRNA attaches to ribosome subunit
and binds to mRNA
Anticodon of tRNA binds to codon
of mRNA
The GENETIC CODE
Translation 4. tRNA drops off amino
process
acid its carrying
5. Another tRNA comes and
drops an amino acid off
The GENETIC CODE
Translation 6. Another tRNA enters, first
process
tRNA leaves
The GENETIC CODE
Translation 7. Each amino acid bonded
process
to previous one to form a
chain
8.
tRNA detaches leaving
amino acid attached to
remaining tRNA
The GENETIC CODE
Translation 9. Repeats until ribosomal
process
subunit reaches stop codon
10. Newly made protein is
released
TRANSLATION
TRANSLATION
TRANSLATION
TRANSLATION
TRANSLATION
Assessment One
Distinguish two differences between RNA
structure and DNA structure
Explain how RNA is made during transcription
Interpret the genetic code to determine the
amino acid coded for by the codon CCU
Compare the roles of the three different types
of RNA during translation
What is the maximum number of amino acids
that could be coded for by a section of mRNA
with the sequence GUUCAGAACUGU?
Protein Synthesis
Protein
Synthesis in
Prokaryotes
Requires too much energy
and too many materials for
cell to make every protein
encoded for by the DNA at
all times
Gene expression can be
regulated according to cell
needs
Ex: E. coli bacteria
Regulating Protein Synthesis
Lac
Operon
1. Lactose in dairy products
enters your intestines
2. E. coli there can use
lactose for nutrition (to make
glucose and galactose)
Regulating Protein Synthesis
• Lac
Operon
• 3. Three genes for breaking down
lactose located next to each other on
DNA (can turn them on or off)
– Genes on: they’re ready to be
transcribed and translated
Regulating Protein Synthesis
Lac
Operon
4. These 3 genes turn on in
presence of lactose and turn
off in its absence
Regulating Protein Synthesis
Lac
Operon
5. Operator- area on DNA
(touching start/promoter) that
acts as on and off switch
Can block RNA polymerase from
transcribing
Regulating Protein Synthesis
Lac
Operon
6. Operon consists of
Operator
Promoter
Three genes
All work together to control
lactose metabolism
Regulating Protein Synthesis
Lac
Operon
7. No lactose present
Lac operon is turned off when
repressor protein binds to DNA
Repressor blocks RNA polymerase
from binding
Regulating Protein Synthesis
Lac
Operon
8. In presence of lactose
Lactose binds to repressor
changing its shape
Causes repressor to fall off DNA
Allows RNA polymerase to bind and
transcribe
Regulating Protein Synthesis
Protein
Most gene regulation is to
synthesis
control the onset of
in
transcription (binding of RNA
eukaryotes
polymerase)
Regulating Protein Synthesis
Protein
Transcription Factorssynthesis
regulatory proteins that help
in
rearrange RNA polymerase
eukaryotes
into the correct position
Intervening DNA
Intervening 1. Introns- longs segments
DNA in
of nucleotides with no coding
Eukaryotic
information
Genes
Break up DNA/genes
Intervening DNA
Intervening 2. Exons- actual genes that
DNA in
are translated into proteins
Eukaryotic
Genes
Intervening DNA
Intervening 3. After transcription, introns
DNA in
in mRNA are cut out by
Eukaryotic
spliceosomes
Genes
Exons are stitched back together
Intervening DNA
Intervening 4. Large numbers of exons
DNA in
and introns allows
Eukaryotic
evolutionary flexibility
Genes
because they can be
shuffled about to make new
genetic codes
Mutations
Mutations
Changes in DNA of a gene
are rare
When in body cells, only
affect individual
When in gametes, offspring
can be affected
Mutations
Mutations
A. Gene rearrangementsentire gene moved to a new
location (disrupts its function)
Mutations
Mutations
B. Gene alterationschanges a gene
Usually results in wrong amino acid
being hooked into protein (disrupts
protein function)
Mutations
Mutations
C. Point Mutation- single
nucleotide changes
Mutations
Mutations
D. Insertion Mutation- extra
piece of DNA is inserted
Mutations
Mutations
E. Deletion Mutationsegments of gene are lost
Mutations
Mutations
F. Frame shift Mutationscauses gene to be read in
wrong 3 nucleotide
sequence
Ex THE CAT ATE
Remove C
THE ATE TE (makes no sense)
WEBSITES
 DNA Workshop
 Transcription
 Interactive Transcribing and Translating a Gene
 Protein Synthesis Animation
 Transcription Animation
 Translation Movie
 Protein Translation Animation
 Animation of Translation
 Protein Synthesis Movie
 Transcription Game
 Protein Synthesis Tutorial