Download Biology

Biology
Chapter 12
DNA and RNA
Unit 12.1
Unit 12.2
Unit 12.3
Unit 12.4
Unit 12.5
DNA
In class assignment.
1. Draw four different symbols (i.e. Ω ∆ π•).
2. Write down any five letter word.
3. Develop a code for the five letters of that word
using only your four symbols. How can you code for
five different letters with only four different symbols?
4.How many different letters can you code for using
only two of your symbols to stand for each letter.
5. How many different letters could you code for using
a string of three symbols for each letter?
DNA
Essential Questions of mid 1900’s
How do genes work?
What are they made of?
Are genes single molecules or longer structures
made up of many molecules?
WHAT IS THE CHEMICAL
NATURE OF THE GENE?
DNA
1928 Frederick Griffith - How do
pneumonia make people sick?
Two strains of bacteria
smooth strain - caused disease
rough edges - no disease
DNA
1928 Frederick Griffith - How do pneumonia make people sick?
Two strains of bacteria
smooth strain - caused disease
rough edges - no disease
Griffith’s Experiment
Thought that poison killed mice
But heat-killed smooth bacteria didn’t kill mice
Transformation
Griffith mixed dead smooth cell bacteria
with live rough bacteria
Mice died
Somehow the rough bacteria had been transformed
DNA
Heat-killed,
disease-causing
bacteria (smooth
colonies)
Disease-causing
bacteria (smooth
colonies)
Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria
(smooth colonies)
Control
(no growth)
Harmless bacteria
(rough colonies)
DNA
Heat-killed,
disease-causing
bacteria (smooth
colonies)
Disease-causing
bacteria (smooth
colonies)
Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria
(smooth colonies)
Dies of pneumonia
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
DNA
Griffith’s Experiment
Thought that poison killed mice But heat-killed smooth bacteria didn’t kill mice
Transformation
Griffith mixed dead smooth cell bacteria
with live rough bacteria; Mice died
Somehow the rough bacteria had been transformed
Avery and DNA
Repeated Griffith’s experiment
Treated extract with enzymes to destroy
proteins, lipids, carbohydrates, RNA
Transformation still occurred
Finally broke down DNA
No transformation occurred
DNA
Avery and DNA
Repeated Griffith’s experiment
Treated extract with enzymes to destroy proteins, lipids, carbohydrates, RNA
Transformation still occurred
Finally broke down DNA; no transformation occurred
AVERY AND OTHERS DISCOVERED THAT DNA STORES AND
TRANSMITS GENETIC INFORMATION
HERSHEY-CHASE EXPERIMENT
1952 Alfred Hershey & Martha Chase
Bacteriophages (bacteria eaters)
Used radioactive markers phosphorus-32 and sulfur35
Phosphorus only in DNA, Sulfur only in protein
Showed DNA, not protein was genetic material
DNA
QuickTime™ and a
Sorenson Video 3 decompressor
are needed to see this picture.
DNA
Structure of DNA
•Must carry genetic information to new generations
•Must be easily copied
Polymer DNA
Monomer - nucleotide
deoxyribose (sugar)
phosphate group
nitrogenous base
adenine & guanine are purines
cytosine & thymine are pyrimidines
By early 1950’s scientists wondered how DNA, just
a string of nucleotides could be the genetic code
DNA
Structure of nucleotides
Purines
Adenine
Guanine
Phosphate group
Pyrimidines
Cytosine
Thymine
Deoxyribose
Chargaff’s Rule
Source of DNA
A
DNA
T
G
C
Streptococcus 29.8
31.6
20.5
18.0
Yeast
31.3
32.9
18.7
17.1
Herring
27.8
27.5
22.2
22.6
Human
30.9
29.4
19.9
19.8
Erwin Chargaff discovered
•percentages of G and C are almost equal
•percentages of A and T are almost equal
Chargaff’s Rule
DNA
Erwin Chargaff discovered
•percentages of G and C are almost equal
•percentages of A and T are almost equal
X-Ray Evidence
Early 1950’s Rosalind Franklin
X-ray diffraction
X-shaped pattern showed twisted
or helix shape
DNA
The Double Helix
Francis Crick and James Watson
Made cardboard and wire models
When they say Franklin’s X-ray pattern the light came
on:
Credited with the double-helix model
Two strands wound around each other
BASE PAIRING - explained Chargaff’s
rule A bonds to T
G bonds to C
Base
Pairing
DNA
Key
Sugar-phosphate
backbone
Adenine (A)
Thymine (T)
Cytosine (C)
Nucleotide
Guanine (G)
Base
Pairing
DNA
Page 294
Nucleotide
Key
Adenine (A)
Sugar-phosphate
backbone
Thymine (T)
Cytosine (C)
Guanine (G)
The Double Helix
Francis Crick and
James Watson, 1953
DNA
DNA
Page 294
The Double Helix
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
12.2Chromosomes and RNA Replication
Goals
•Summarize the events of DNA
replication
•Relate the DNA molecule to
chromosome structure
12.2Chromosomes and RNA Replication
DNA and Chromosomes
Prokaryotes: One circular DNA molecule
12.2Chromosomes and RNA Replication
DNA and Chromosomes
Prokaryotes: One circular DNA molecule
Eukaryotes: 1,000 times as much DNA
DNA found in nucleus
Organized into chromosomes
46 in human beings
8 in drosophila
22 in redwood trees
12.2Chromosomes and RNA Replication
DNA length
E. Coli
4,639,221 base pairs
1.6 millimeters
inside a 1.6µm (1/1,000 of a mm)
imagine 1m yarn inside 1mm ball
12.2Chromosomes and RNA Replication
Chromosome Structure
Eukaryote DNA packed more tightly
Human chromosome > 30 million base
pairs
A human cell has more than
1METER of DNA!
How does it all fit?
12.2Chromosomes and RNA Replication
Chromosome Structure
A human cell has more than
1METER of DNA!
How does it all fit?
DNA and protein(histones) pack together
into bead-like nucleosomes which coil into
tight loops and coils chromatin
Chromatin is dispersed until cell division
when chromosomes form
12.2Chromosomes and RNA Replication
Chromosome Structure
A human cell has more than 1METER of DNA! How does it all fit?
DNA and protein(histones) pack together into bead-like
nucleosomes which coil into tight loops and coils chromatin
Chromatin is dispersed until cell division when chromosomes
form
12.2Chromosomes and RNA Replication
DNA Replication
Two strands are, “complimentary”
You could construct one strand from
the other (remember base-pairing)
DNA separates into two strands
Each strand is a model for a duplicate
complimentary strand
12.2Chromosomes and RNA Replication
DNA Replication
DNA separates into two strands
Each strand is a model for a duplicate
complimentary strand
Enzymes unzip the molecule
DNA polymerase
Nucleotides are arranged on the
template strand.
12.2Chromosomes and RNA Replication
DNA Replication
Page 298
Quiz 1
15 points
3 questions
5 points for each question
You will need a piece of paper and a pen or
pencil. Get those out now.
You may use your notes; please put books neatly
away
This paper must have a standard heading at the
top of the page, full name, date, and period
Yes, neatness does count.
Drawings must be clearly labeled
1. Make a drawing or several drawings of DNA
that demonstrate your understanding of its basic
structure. Be sure to include and label the sugarphosphate backbone, base pairing and double
helix. Correctly show the relationship between
the Adenine, Thymine, Guanine, and Cytosine
2. Make a labeled drawing and explain how
DNA is replicated
3. Describe one of the experiments that
demonstrated that DNA is the substance that
carries genetic information.
12.RNA and Protein Synthesis
Essential Questions
•How does RNA differ from DNA?
•What are the different types of RNA?
•What is transcription of RNA?
•What is the genetic code?
•Explain translation
•What is the relationship between genes
and protein?
Click for a great animation
12.RNA and Protein Synthesis
1.A part of the genetic code is copied
from DNA to mRNA
2.RNA carries out process of making
proteins
12.RNA and Protein Synthesis
“The Central Dogma”



The information encoded with the DNA
nucleotide sequence of a double helix
is transferred to a mRNA molecule.
The mRNA molecule travels out of the
nucleus and attaches to a ribosome
Using the RNA nucleotide sequence
and the genetic code, the ribosome
assembles a protein
12.RNA and Protein Synthesis
TRANSCRIPTION



DNA stays in the nucleus
mRNA is copied from DNA and sent out
into the cytoplasm
Animations:
Transcription showing full complex
Transcription – cool sounds
12.RNA and Protein Synthesis
The Central Dogma (brief)
• DNA is copied to
mRNA
• mRNA is used as
blueprint to make
protein
12.RNA and Protein Synthesis
Structure of RNA
•RNA’s sugar backbone contains ribose
instead of deoxyribose
•RNA is like one strand of the DNA
double-helix
•RNA uses uracil instead of Thymine
12.RNA and Protein Synthesis
•RNA’s sugar backbone contains ribose instead of
deoxyribose
•RNA is like one strand of the DNA double-helix
•RNA uses uracil instead of Thymine
Types of RNA
PROTEIN SYNTHESIS
•Messenger RNA brings a copy of gene
code from nucleus to cytoplasm
•Ribosomal RNA
•Transfer RNA transfers code to protein
12.RNA and Protein Synthesis
PROTEIN SYNTHESIS
•Messenger RNA brings a copy of gene code from nucleus to
cytoplasm
•Ribosomal RNA
•Transfer RNA transfers code to protein
Transcription
•RNA polymerase separates strands
•makes a transcript of one strand on mRNA
•Promoters tell RNA polymerase where to
start transcribing
tRNA - transfer
•
Specified amino acids are attached to
tRNA
•
each anti-codon corresponds to the
amino acid specified by the genetic code
•
Each tRNA has an anti-codon (3
nucleotides)
•
Anti-codon region base pairs with
mRNA trascript
12.RNA and Protein Synthesis
RNA polymerase separates strands
•makes a transcript of one strand on mRNA
•Promoters tell RNA plymerase where to start transcribing
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
RNA
DNA
12.RNA and Protein Synthesis
RNA polymerase separates strands
•makes a transcript of one strand on mRNA
•Promoters tell RNA plymerase where to start transcribing
RNA Editing
Some editing takes place once RNA is
transcribed
•Introns - sections of mRNA to are cut
out
•Exons - spliced back together to form
final mRNA
12.RNA and Protein Synthesis
•Introns - sections of mRNA to are cut out
•Exons - spliced back together to form final mRNA
Genetic Code
Polymer - protein
Monomer - amino acid (there are 20
possibilities)
codon - 3 nucleotides codes for each
amino acid
12.RNA and Protein Synthesis
Polymer - protein
Monomer - amino acid (there are 20 possibilities)
3 nucleotides = 1 codon - codes for each amino acid
Translation
Assembly happens in ribosome
Transfer RNA anticodon matches to
mRNA codon and brings attached
amino acid
Polypeptide chain grows until STOP
codon is reached
12.RNA and Protein Synthesis
Assembly happens
in ribosome
Transfer RNA
anticodon matches
to mRNA codon
and brings attached
amino acid
Polypeptide chain
grows until STOP
codon is reached
12.RNA and Protein Synthesis
Assembly happens
in ribosome
Transfer RNA
anticodon matches
to mRNA codon
and brings attached
amino acid
Polypeptide chain
grows until STOP
codon is reached
12.RNA and Protein Synthesis
Assembly happens in ribosome
Transfer RNA anticodon matches to mRNA codon
and brings attached amino acid
Polypeptide chain grows until STOP codon is reached
Roles of DNA / RNA
DNA - master plan
kept safe in nucleus
RNA - working blueprints
brought out to cytoplasm
12.RNA and Protein Synthesis
DNA - master plan
kept safe in nucleus
RNA - working blueprints
brought out to cytoplasm
Genes and Proteins
Genes code proteins
Proteins are enzymes
catalyze chemical reactions
Color, antigens, blood type
Proteins are the key
12.RNA and Protein Synthesis
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
12.RNA and Protein Synthesis
animations
• Translation
• Translation – no sound, basic
CODE Breaker Activity
Four Roles
•DNA - Agent DiNA
Provides code to be broken
•mRNA - Agent miRNA
Translates code for Agent tuRNA
•tRNA - Agent tuRNA picks up code
delivers it to
•rRNA - Agent R.B.Some
compiles information
CODE Breaker Activity
Step 1
DNA - Agent DiNA
•counts 3 numbers starting from left
•cuts 1 group
•passes it off to Agent miRNA
•only 1 group of 3 may be cut at a time
CODE Breaker Activity
Step 2
mRNA - Agent miRNA
• Using secret table code, Agent
miRNA decodes and translates to a
letter
•Relays letter information to Agent
tuRNA
CODE Breaker Activity
Step 3
tRNA - Agent tuRNA
• Gets letter information from Agent
miRNA
•Turns letter over to R.B.Some
CODE Breaker Activity
Step 3
R.B.Some
• Assembles letters
After step four is completed,
REPEAT
Until code is broken
12.4 Mutations
Cells make mistakes
1. Copy the following information about Protein X: Methionine—
Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP.
2. Use Figure 12–17 on page 303 in your textbook to determine
one possible sequence of RNA to code for this information.
Write this code below the description of Protein X. Below this,
write the DNA code that would produce this RNA sequence.
3. Now, cause a mutation in the gene sequence that you just
determined by deleting the fourth base in the DNA sequence.
Write this new sequence.
4. Write the new RNA sequence that would be produced. Below
that, write the amino acid sequence that would result from this
mutation in your gene. Call this Protein Y.
5. Did this single deletion cause much change in your protein?
Explain your answer.
12.4 Mutations
Cells make mistakes
Mutate - to change
•Gene mutations are changes in a
single gene
•Chromosomal mutations involve
changes in whole chromosomes
12.4 Mutations
Gene Mutations
Point mutations
change in one nucleotide
•Substitution changes 1 amino acid
•Frameshift mutation
insertion or deletion of one nucleotide
throws off subsequent codons
can prevent functioning of gene
12.4 Mutations
Gene Mutations
12.4 Mutations
Gene Mutations
12.4 Mutations
Chromosomal Mutations
Change in number or structure
of chromosomes
•deletion
•duplication
•inversion
•translocation
12.5 Gene Regulation
Every cell in your body, with the exception of
gametes, or sex cells, contains a complete copy of
your DNA. Why, then, are some cells nerve cells with
dendrites and axons, while others are red blood cells
that have lost their nuclei and are packed with
hemoglobin? Why are cells so different in structure
and function? If the characteristics of a cell depend
upon the proteins that are synthesized, what does
this tell you about protein synthesis? Answer the
1. questions
Do you think
thatfollow:
cells produce all the proteins for which the DNA (genes)
that
code? Why or why not? How do the proteins made affect the type and function of cells?
2.
Consider what you now know about genes and protein synthesis. What might
be some ways that a cell has control over the proteins it produces?
3.
What type(s) of organic compounds are most likely the ones that help to
regulate protein synthesis? Justify your answer.
12.5 Gene Regulation
Every cell in your body, with the exception of gametes, or sex cells,
contains a complete copy of your DNA. Why, then, are some cells nerve
cells with dendrites and axons, while others are red blood cells that have
lost their nuclei and are packed with hemoglobin? Why are cells so different
in structure and function? If the characteristics of a cell depend upon the
proteins that are synthesized, what does this tell you about protein
synthesis? Answer the questions that follow:
1.
Do you think that cells produce all the proteins for which
the DNA (genes) code? Why or why not? How do the proteins
made affect the type and function of cells?
2.
Consider what you now know about genes and protein
synthesis. What might be some ways that a cell has control over
the proteins it produces?
3.
What type(s) of organic compounds are most likely the
ones that help to regulate protein synthesis? Justify your answer.
12.5 Gene Regulation
Goals
Describe a typical gene
Describe how the lac genes are
turned on and off
Explain how most eukaryotic genes
are controlled
Relate gene regulation to
development
12.5 Gene Regulation
Gene Expression
Not every gene is expressed in
every cell
Cells in your finger don’t produce amylase
Promoters tell RNA to start
transcription
What are the regulatory sites next to
the promoter ?
12.5 Gene Regulation
Gene Expression
Not every gene is expressed in every cell
Cells in your finger don’t produce amylase
Promoters tell RNA to start transcription
What are the regulatory sites next to the promoter ?
Gene Regulation: An Example the lac operon
In E. coli 3 genes are turned on and off together
Operon - genes that operate together
These 3 genes help E. coli use lactose lac operon
12.5 Gene Regulation
Gene Regulation: An Example the lac operon
In E. coli 3 genes are turned on and off together
Operon - genes that operate together
These 3 genes help E. coli use lactose - lac operon
Lac operon codes for proteins that
take lactose across the cell membrane
break lactose up into galactose and glucose
The lac operon genes are turned on by the
presence of lactose
Beside the 3 lac operon genes are two other
regions
Promoter
Operator
12.5
Gene
Regulation
Lac operon codes for proteins that
take lactose across the cell membrane
break lactose up into galactose and glucose
The lac operon genes are turned on by the presence of lactose
Beside the 3 lac operon genes are two other regions
Promoter
Operator
When RNA polymerase gets to the promoter, it
transcriptions begins
The operator blocks it by binding to a protein
called the lac repressor
BUT if lactose binds to the repressor, it falls off
allowing RNA polymerase to begin
transcription
12.5 Gene Regulation
When RNA polymerase gets to the promoter, it transcriptions
begins
The operator blocks it by binding to a protein called the lac
repressor
BUT if lactose binds to the repressor, it falls off
allowing RNA polymerase to begin transcription
Eukaryotic Gene Regulation
Operons are not used
Genes are controlled individually
Regulatory sequences more complex than lac
TATATA or TATAAA region
“TATA Box” helps position RNA polymerase
Found just before eukaryotic promoters
12.5
Gene
Regulation
Eukaryotic Gene Regulation
Operons are not used
Genes are controlled individually
Regulatory sequences more complex than lac
TATATA or TATAAA region
“TATA Box” helps position RNA polymerase
Found just before eukaryotic promoters
Many, “enhancer,” sequences found in
eukaryotes
•unwind tightly twisted chromatin
•attract RNA polymerase
•block access (like prokaryote repressor proteins)
12.5 Gene Regulation
Many, “enhancer,” sequences found in eukaryotes
•unwind tightly twisted chromatin
•attract RNA
polymerase
90
•block access
80 (like prokaryote repressor proteins)
70
Regulatory
60
sites50
Promoter
(RNA polymerase binding site)
40
30
Start
transcription
20
10
0
1st Qtr
2nd Qtr
3rd Qtr
DNA strand
East
West
North
Stop transcription
4th Qtr
12.5 Gene Regulation
Many, “enhancer,” sequences found in eukaryotes
•unwind tightly twisted chromatin
•attract RNA polymerase
•block access (like prokaryote repressor proteins)
WHY IS THE SYSTEM SO COMPLEX IN
EUKARYOTES
•Complex multicellular organisms
•All cells carry the code
•Each cell uses only a tiny fraction of the code
12.5 Gene Regulation
WHY IS THE SYSTEM SO COMPLEX IN EUKARYOTES
•Complex multicellular organisms
•All cells carry the code
•Each cell uses only a tiny fraction of the code
Regulation and Development
“hox genes” control embryo development
Which cells develop into what
Master control genes
Fruit fly legs growing in the place of antennae
Copy of mouse eye growth gene inserted into
drosophila leg caused fruit fly to grow an eye on
its knee! Onward to Genetic Engineering next week