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Chapter 12: DNA & RNA
What do you already know about DNA?
DNA Clearly Stated
12.1 Three important functions of DNA
1. Store genetic information – stores genes
2. Copy information – copy genes prior to cell division
3. Transmit the information – pass genetic information along to next generation
12.2 Structure of DNA• DNA = Deoxyribonucleic Acid• A nucleotide is composed of:
1. Sugar (deoxyribose)2. Phosphate group3. Nitrogenous Base
• A nucleotide is the monomer of a DNA strand (polynucleotide):
DNA polynucleotide
A
C
T
G
T
Sugar-phosphate backbone
Phosphate group
Nitrogenous base
SugarA
C
T
G
T
Phosphategroup
O
O–
OO P CH2
H3C C
C
C
CN
C
N
H
H
O
O
C
O
O
H
C H H
H
C
H
Nitrogenous base(A, G, C, or T)
Thymine (T)
Sugar(deoxyribose)
DNA nucleotide
DNA nucleotide
12.2 Structure of DNA
DNA is a double-stranded helixJames Watson and Francis Crick
• Worked out the three-dimensional structure of DNA, based on photos by Rosalind Franklin
12.2 Structure of DNA
The structure of DNA• Consists of two polynucleotide strands wrapped
around each other in a double helix (twisted ladder)
Twist
12.2 Structure of DNA
Hydrogen bonds (weak) between bases• Hold the strands together
Each base pairs with a complementary partner• A with T, and G with C
G C
T A
A T
G
G
C
C
A T
GC
T A
T A
A T
A T
G C
A T
O
O
OH–O
P
OO
–OPO
OO
P– O
– O OP
OO
O
OH
H2C
H2C
H2C
H2C
O
O
O
O
O
O
O
O
PO–
O–
O–
O–
OH
HO
O
O
O
P
P
P
O
O
O
O
O
O
O
O
T A
G C
C G
A T
CH2
CH2
CH2
CH2
Hydrogen bond
Basepair
Ribbon model Partial chemical structure Computer model
12-3 DNA Replication
When does DNA replicate?– DNA must copy before cell division (mitosis)
How does it replicate?
1. DNA is separated by helicase (enzyme)
2. Nucleotides are added according to base pairing rules, using DNA polymerase (enzyme).
A T
C G
G C
A T
T A
A T
C G
G C
A T
T A
A T
C G
G C
A T
T A
A T
C G
G C
A
T
A T
C G
AC
T
A
Parental moleculeof DNA
Both parental strands serve as templates
Two identical daughtermolecules of DNA
12-3 DNA Replication
DNA replication is semi-conservative
1. The parent strand becomes two daughter strands.
2. Each daughter strand is composed of one half the parent (old strand) and one half new.
Origin of replication
Two daughter DNA molecules
Parental strand
Daughter strand
Bubble
DNA Replication Video
– The DNA of the gene is transcribed into RNA• Which is translated into protein
• The flow of genetic information from DNA to RNA to Protein
DNA
Transcription
RNA
Protein
Translation
Chapter 13 Protein Synthesis - Overview
Central Dogma - FLOW IS FROM DNA TO RNA TO PROTEIN
Chapter 13 Protein Synthesis (Overview)
FLOW IS FROM DNA TO RNA TO PROTEIN
• Genes on DNA are expressed through proteins, which provide the molecular basis for inherited traits
• A particular gene, is a linear sequence of many nucleotides
– Specifies a protein made of amino acids
Chapter 13 Protein Synthesis (Overview)
Genes - discrete units of hereditary information comprised of a nucleotide sequence found in a DNA molecule.
Chapter 13 Protein Synthesis (Overview)
13.1 RNAThree Types of RNA
• Messenger RNA (mRNA) – carries copies of genes (DNA) to the rest of the cell.
• Ribosomal RNA (rRNA) – make up the ribosomes.
• Transfer RNA (tRNA) – transfers the amino acids to the ribosomes as specified by the mRNA
12-1 Messenger (mRNA)
1. Three main differences between mRNA and DNA
• Ribose instead of deoxyribose• mRNA is single stranded• mRNA has uracil in place of thymine (U
instead of T)
12.1 TRANSCRIPTION: The process of making mRNA from DNA
– Why do you need this process?• Location of DNA?
Nucleus
• Location of Ribosome? Cytoplasm
– mRNA takes code from DNA in the nucleus to the cytoplasm
T A C T T C A A A A T C
A T G A A G T T T T A G
A U G A A G U U U U A G
Transcription
Translation
RNA
DNA
Met Lys PhePolypeptide
Startcondon
Stopcondon
Strand to be transcribed
12-3 Protein Synthesis - Translation
• Translation is defined as going from mRNA to protein– tRNA which have amino acids attached are
going to the ribosome in the cytoplasm.• What are amino acids? monomers of
proteins• Does the order of amino acids matter? Yes,
they must be in order for the protein to fold correctly.
Amino acid attachment site
– How does the correct tRNA (with amino acid attached) bind to the mRNA? The tRNA contains an anticodon which matches up with the mRNA sequence (codon).
– Translation at Ribosome
Amino acid attachment site
Hydrogen bond
RNA polynucleotide chain
AnticodonAnticodon
Amino acid attachment site
Transfer RNA (tRNA) molecules serve as interpreters during translation
tRNAmolecules
mRNA Small subunit
Growingpolypeptide
Largesubunit
Animation
1. Take the DNA and transcribe it into mRNAExample: TAC ATA CTA GCG ACT
mRNA:
2. Take the mRNA sequence and decode it using the codon chart.
AUG UAUGAU CGC UGA
AUG = METUAU = TYRGAU = ASPCGC = ARG
Figure out the exact sequence of amino acids needed
13.3 Mutations• Mutations – heritable changes in genetic information (changes to the
DNA sequence)
• Two types - gene and chromosomal mutations
• Mutations can be caused by chemical or physical agents (mutagens)– Chemical – pesticides, tobacco smoke, environmental pollutants
– Physical – X-rays and ultraviolet light
13.3 Mutations• Gene mutations
– Point Mutation: mutations that affect a single nucleotide
– Frameshift mutation: shift the reading frame of the genetic message.
• Can change the entire protein so it doesn’t work
• Gene Mutations Explained
13.3 Mutations
13.3 Chromosomal Mutations• Chromosomal mutation: mutation
that changes the number or structure of chromosomes.
13.3 Chromosomal Mutations• Types of chromosomal mutations:
– Deletion: The loss of all or part of a chromosome
– Duplication: A segment is repeated
– Inversion: part of the chromosome is reverse from its usual direction.
– Translocation: one chromosome breaks off an attaches to another chromosome.
1. Each person, Construct the DNA Strand Below2. Then, construct the complimentary strand to make a complete DNA molecule3. Ignore the color scheme below. Use:
Cytosine = Blue Deoxyribose Sugar = Black PentagonThymine = Green Phosphate = White TubesAdenine = Orange Ribose Sugar = Purple PentagonGuanine = Yellow tRNA = Purple PlasticUracil = Purple Amino Acid = Black Plastic
4. When you have constructed the complementary strand join the two strands together with Hydrogen bonds
DNA Modeling
1. Each group will construct an mRNA strand from the DNA strand below2. Then, take your mRNA strand outside the nucleus to the ribosome3. Use the codons of mRNA and anticodons of tRNA to manufacture proteins4. Use the following model pieces:
Cytosine = Blue Deoxyribose Sugar = Black PentagonThymine = Green Phosphate = White TubesAdenine = Orange Ribose Sugar = Purple PentagonGuanine = Yellow tRNA = Purple PlasticUracil = Purple Amino Acid = Black Plastic
Peptide Bonds (between AAs) – Grey Tubes
5. When you have constructed the complementary strand join the two strands together with Hydrogen bonds
Transcription and Translation Modeling
Making a DNA Molecule
• Must Contain– Deoxyribose Sugar – Pentagon shape– Phosphate Group – Circle– At least 6 base pairs (complimentary base pair
must be interlocking)– Label all parts of the DNA– Question: How could the structure of a DNA
molecule allow it to carry information and replicate (make copies of itself).
Backbone
Phage attachesto bacterial cell.
Phage injects DNA. Phage DNA directs hostcell to make more phageDNA and protein parts.New phages assemble.
Cell lyses and releases new phages.
HIV Images – NPR Story Toddler
DNA – Structure Questions
1.What pair of scientists are largely credited for discovering the shape of the DNA molecule?
2.Name the scientist whose photographs helped solve the mystery of DNA’s structure
3.DNA is in the shape of a _______ _______.
4.What are the sides of the DNA molecule made of? (2 things)
5.What are the rungs of the ladder made of?
6.What is the monomer of DNA?
7.What holds nitrogenous bases together?
DNA – early scientists
• Scientist/Experiments– What did Griffith call the phenomenon he
observed in the mouse experiment?– What did Hershey and Chase mark the
bacteriophage with? What parts were marked?– How did marking the bacteriophage assist in
determining DNA was the transforming factor?
Bryson Reading – Discovery of DNA
Section 1.a. Why is it surprising that the scientists working
in England even discovered the structure of DNA?
b. When did Watson start college and when did he get his Ph.D.?
Section 2.a. Why was understanding the shape of DNA so
important?b. What did Watson remark about that is surprising
in his autobiography?
Bryson Reading – Discovery of DNA
Section 3.a. How did Watson depict Rosie Franklin in his book
The Double Helix?b. What did Rosie Franklin have that at the time was
the best in the field? c. What method was Franklin using to capture DNASection 4.a. How were women treated at Kings College?b. What did Franklin do to throw her colleagues off the
trail?c. How did Watson and Crick eventually see Franklin’s
photos?
Central Dogma Questions1.The flow of genetic information is from ______ to ______
to ______.
2.Why does DNA send a “messenger” out into the cytoplasm?
3.The manufacture of mRNA from DNA is called _____________.
4.What cellular organelle uses the DNA codes to manufacture proteins?
5.How is DNA ultimately associated with our phenotype or outward appearance?
Homework Chapter 13 Sections 13.3 and 13.4
Section 13.3 Mutations 372-376 a. Explain the difference between the three types of “point”
mutations?
a. How do point mutations differ from chromosomal mutations?
a. Explain how mutations could be harmful or beneficial
Section 13.4 Gene Regulation and Expression 377-383a. Describe how prokaryotes turn lac genes on and off (mention:
promoters, operators, lactose, repressor, and RNA polymersase)?
a. How do eukaryotes regulate genes during transcription?
a. What do homeotic genes like homeobox and hox genes have to do with development? What is the difference between homeobox and hox genes?
Twist
Drawing a DNA Molecule
• Must Contain– Deoxyribose Sugar – Pentagon shape– Phosphate Group – Circle– At least 6 base pairs (complimentary base pair
must be interlocking)– Label all parts of the DNA– Question: How does the structure of a DNA
molecule allow it to carry information and replicate.
– Worth 20 Points
Backbone
Please complete the following:– The complementary DNA strand for:
• GACTGAGGA– The mRNA strand for:
• GACTGAGGA– Translate the mRNA sequence to amino acids:
• CCAUUUACG – Translate the mRNA codons to tRNA anticodons:
• CCAUUUACG
Extra Credit:
Biology 1 pts each:
1. What is one part of the cell theory?
2. What are the single units of a polymer called?
Non Bio 2 pts:
Title and artist of these lyrics
3. Aww, he got the velcro!
MutationsFANTASY REALITY
MutationsFANTASY REALITY
