Download No Slide Title

Section 12-1
Section Outline animations

12–1
DNA
A.Griffith and Transformation
1. Griffith’s Experiments
2. Transformation
B.Avery and DNA
C.
The Hershey-Chase Experiment
1. Bacteriophages
2. Radioactive Markers
D.
Go to
Section:
The Structure of DNA
1. Chargaff’s Rules
2. X-Ray Evidence
3. The Double Helix
DNA
What is Morse code? --- -- - --- What is the function?
How do organisms pass on traits to offspring?
Does every cell of your body contain the same amount of DNA?
What about egg and sperm cells?
Does replication of DNA need to be accurate? Why or Why not?
Why is it important to decode any code?
History of DNA discoveries – (very recent –this century)
Griffith ( 1928) - Transformation- one strain of bacteria had been transformed
into another. See experiment.
Can you imagine producing a tiger from a tabby cat? This was a great
breakthrough!
Avery and scientists (1944) – What molecules caused this transformation?
They discovered DNA was the factor that was an influence on heredity.
Hersey and Chase (1952) – Experiments with bacteriophages
(bacteria eaters) showed that DNA was the carrier for the genetic code of
organisms. What did they do?
Rosalind Franklin (1950’s)- Took X-rays of DNA molecules to discover
structure. These were used later by Watson and Crick.
Watson and Crick _ (1953) – Young scientists who discover double helix
shape of DNA. Shared the Nobel Prize in 1962 with Franklin’s assistant
(Franklin had died). Their first models of DNA were of rubber and wooden
balls with sticks in between.
Human Genome Project- What is this?
Section 12-1
Figure 12–2 Griffith’s
Experiment
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
Go to
Section:
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
Section 12-1
Figure 12–2 Griffith’s
Experiment
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
Go to
Section:
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
Figure 12–4 Hershey-Chase
Experiment
Section 12-1
Go to
Section:
Bacteriophage with
phosphorus-32 in
DNA
Phage infects
bacterium
Radioactivity inside
bacterium
Bacteriophage with
sulfur-35 in protein
coat
Phage infects
bacterium
No radioactivity inside
bacterium
Figure 12–4 Hershey-Chase
Experiment
Section 12-1
Go to
Section:
Bacteriophage with
phosphorus-32 in
DNA
Phage infects
bacterium
Radioactivity inside
bacterium
Bacteriophage with
sulfur-35 in protein
coat
Phage infects
bacterium
No radioactivity inside
bacterium
Figure 12–4 Hershey-Chase
Experiment
Section 12-1
Go to
Section:
Bacteriophage with
phosphorus-32 in
DNA
Phage infects
bacterium
Radioactivity inside
bacterium
Bacteriophage with
sulfur-35 in protein
coat
Phage infects
bacterium
No radioactivity inside
bacterium
What is DNA?
-Deoxyribonucleic Acid – Nucleic acid which stores and transmits genetic
information.
Function of DNA – control of the cell and production of proteins in the cell.
*Composed of 3 parts:
1. Phosphate group (P)
2. Nitrogen base – 2 types:
A. Purines – double ring of carbon and nitrogen (adenine and guanine)
guanine
adenine
B. Pyrimidines – single ring of carbon and nitrogen (thymine and cytosine)
cytosine
thymine
3. Sugar group
*A nucleotide is composed of a nitrogen base, phosphate and sugar. Two
complementary nucleotides joined are called a molecule of DNA.
Section 12-1
Go to
Section:
Percentage of
Bases in Four
Organisms
Source of DNA
A
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
Figure 12–5 DNA Nucleotides
Purines
Adenine
Guanine
Phosphate
group
Go to
Section:
Pyrimidines
Cytosine
Thymine
Deoxyribose
Figure 12–7 Structure of DNA
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Go to
Section:
Section 12-2
Interest Grabber
 A Perfect Copy
 When a cell divides, each daughter cell
receives a complete set of chromosomes. This
means that each new cell has a complete set of
the DNA code. Before a cell can divide, the
DNA must be copied so that there are two sets
ready to be distributed to the new cells.
Go to
Section:
Section 12-2
Interest Grabber continued
1. On a sheet of paper, draw a curving or zig-zagging line that
divides the paper into two halves. Vary the bends in the line as
you draw it. Without tracing, copy the line on a second sheet of
paper.
2. Hold the papers side by side, and compare the lines. Do they
look the same?
3. Now, stack the papers, one on top of the other, and hold the
papers up to the light. Are the lines the same?
4. How could you use the original paper to draw exact copies of
the line without tracing it?
5. Why is it important that the copies of DNA that are given to new
daughter cells be exact copies of the original?
Go to
Section:
Section 12-2
Section Outline
12–2Chromosomes and DNA Replication
A. DNA and Chromosomes
1. DNA Length
2. Chromosome Structure
B. DNA Replication
1. Duplicating DNA
2. How Replication Occurs
Go to
Section:
12-2
DNA Replication – This is how new DNA is made for new cells
and for repairing DNA.
DNA- must be copied exactly like blueprints.
It does this by “UNZIPPING” each side of the double helix. DNA
helicase (an enzyme) breaks the hydrogen bonds between
nitrogen bases. Polymerase catalyses the new bonds.
*DNA can be easily damaged by certain things. What are
some of the factors that can damage and change
DNA????
The cells have a built in “proofreading” function. This is taken
care of by enzymes (which are all proteins), in each cell. The
enzymes remove and replace damaged nucleotides to keep
the DNA accurate.
Accuracy must be maintained since the sequence of nitrogen
bases contains the information determining the structure and
function of the entire organism –even humans.
Prokaryotic Chromosome
Structure
Chromosome
E. coli
bacterium
Bases on the
chromosome
Go to
Section:
Figure 12-10 Chromosome Structure of
Eukaryotes
Chromosome
Nucleosome
DNA
double
Coils
Supercoils
Histones
Go to
Section:
helix
Section 12-2
Figure 12–11 DNA Replication
New
strand
DNA
polymerase
Original
strand
DNA
polymerase
Growth
Growth
Replication
fork
Replication
fork
New
strand
Original
strand
Nitrogenous
bases
Section 12-3

Section Outline
12–3 RNA and Protein Synthesis
A. The Structure of RNA
B. Types of RNA
C. Transcription
D. RNA Editing
E. The Genetic Code
F. Translation
G.The Roles of RNA and DNA
H. Genes and Proteins
Go to
Section:
Section 12-3
RNA- Ribonucleic Acid
Function- transmits information for the
manufacture proteins.
DNA never leaves the nucleus, but RNA does.
Structure- RNA is made of nucleotide
monomers (pieces).
How do RNA and DNA differ?
DNA
two strands
deoxyribose sugar
nitrogen base thymine
Go to
Section:
RNA
one strand
ribose sugar
nitrogen base uracil
There are 3 types of RNA that are made in the
nucleus and move to the cytoplasm where
proteins are made.
There are 3 types of RNA that are made in the
nucleus and move to the cytoplasm where proteins
are made.
1. Messenger RNA (mRNA) – This is a single,
uncoiled strand that transmits information from DNA
to be used during protein synthesis (making of
proteins). (Ribbon)
2. Transfer RNA (tRNA) – This is a single strand of
RNA that is folder back like a “hairpin” and some
bases pair with this shape. There are 20 or more
varieties to transfer the amino acids. (Cross)
3. Ribosomal RNA (rRNA)- This is a globular form
(round and blob-like) of RNA that is part of
ribosomes. The true function is not known, but it
aids in the making of proteins. (Round)
How is RNA made in the nucleus?
RNA is made in the nucleus from a process called
Transcription- this is where important information on
the DNA molecule is transferred to a “mobile” form that
can be moved to the cytoplasm.
Protein Synthesis/translation This is how proteins are
made in the cytoplasm. Link
Link 2
How does the cell know which proteins to make?
Where does the information come from?
How does it get to the cytoplasm????????
Proteins are made of strands called polypeptides. Each
polypeptide is composed of many amino acids (aa)
attached to each other.
For a certain protein to be made, the amino acids must be in a
certain sequence.
The genetic code (DNA) is made of nucleotides that are put into a
“mobile form” called RNA (in particular mRNA). MRNA is the
complimentary strand to each DNA strand.
Three nucleotides hooked together are called a codon. (mRNA)
Each codon (a-u-g, g-c-c, u-g-a) recognizes a certain amino
acid.
A chart for amino acids that are recognized by mRNA condons are
found in the text.
For example a codon for u-u-c codes for the amino acid alanine.
The codon a-c-g codes for threonine.
These codons are in a special order to code for the order of the
amino acids to produce proteins.
Translation- see diagrams for steps to help you understand
process
Figure 12–14 Transcription
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
RNA
polymerase
DNA
RNA
Go to
Section:
Section 12-3
Concept Map
RNA
can be
Messenger RNA
also called
Ribosomal
RNA
which functions
to
mRNA
also called
which functions to
rRNA
Combine
with proteins
Carry
instructions
from
to
to make up
DNA
Ribosome
Ribosomes
Transfer
RNA
also called
which functions to
tRNA
Bring
amino acids to
ribosome
Figure 12–18 Translation
Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
Phenylalanine
tRNA
The mRNA then enters the cytoplasm and
attaches to a ribosome. Translation begins at
AUG, the start codon. Each transfer RNA has
an anticodon whose bases are complementary
to a codon on the mRNA strand. The ribosome
positions the start codon to attract its
anticodon, which is part of the tRNA that binds
methionine. The ribosome also binds the next
codon and its anticodon.
Ribosome
Go to
Section:
mRNA
Transfer RNA
Methionine
mRNA
Lysine
Start codon
Figure 12–18 Translation
(continued)
The Polypeptide “Assembly Line”
The ribosome joins the two amino acids—
methionine and phenylalanine—and breaks
the bond between methionine and its tRNA.
The tRNA floats away, allowing the ribosome
to bind to another tRNA. The ribosome moves
along the mRNA, binding new tRNA molecules
and amino acids.
Lysine
Growing polypeptide chain
Ribosome
tRNA
tRNA
mRNA
Completing the Polypeptide
mRNA
Ribosome
Go to
Section:
Translation direction
The process continues until the ribosome reaches
one of the three stop codons. The result is a
growing polypeptide chain.
Figure 12–17 The Genetic Code
Go to
Section:
Section 12-4

Section Outline
12–4 Mutations
A. Gene Mutations
B. Chromosomal Mutations
 Determining the Sequence of a Gene
 DNA contains the code of instructions for
Go to
Section:
cells. Sometimes, an error occurs when
the code is copied. Such errors are called
mutations.
Section 12-4
Interest Grabber continued
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.
Go to
Section:
Mutations are one of the factors that cause a change in a population.
Most are random. Interactions between genes and the environment are
extremely important.
Mutations-mistakes made in duplicating genetic information.
Types:
1. Germ mutations- occur in the sex cells
2. Somatic mutations - occur in other body cells. These are not
inheritable (cancer)
Gene Mutations – involve changes in the nucleotides.
Types of gene mutations:
point mutation – one nucleotide affected
Frameshift mutation – deleted or inserted nucleotide
Chromosome mutations - when there is a change in the number or
structure of chromosomes.
4 Types: deletions, duplications, inversion and translocation
(see diagrams)
Gene Regulation
*Gene interactions (Recessive vs. Dominant) recessive
genes do not produce the enzyme (protein) for a trait to
be demonstrated.
Gene expression - genes are not activated at the same
time or in the same way. When a product of a gene is
being made (protein) the gene is said to be expressed.
How does a cell know which genes to turn on?
Example
Caterpillar - What determines the appearance of a type of
caterpillar?
*Some caterpillars are changed by the food they eat.
(Some look like leaves and others like twigs)
*Does the food you eat have the same effect on you?
Gene Mutations:
Substitution, Insertion, and Deletion
Section 12-4
Deletion
Substitution
Go to
Section:
Insertion
Section 12-4
Figure 12–20 Chromosomal
Mutations
Deletion
Duplication
Inversion
Translocation
Go to
Section:
Section 12-5
12–5
Section Outline
Gene Regulation
A. Gene Regulation: An Example
B. Eukaryotic Gene Regulation
C. Regulation and Development
Regulation of Protein Synthesis
How does the DNA differ in your muscle cell and skin cells?
How about a nerve cell and liver cell?
Does every cell do the same job?
How does each cell control what it does?
Go to
Section:
Section 12-5
Things which affect genes:
Radiation, hormones, temperature, light conditions in cells, other genes,
chemicals, nutrition
Operon - gene cluster including the following parts:
Inducer - starts the activity of the genes. Proteins are produced.
Repressor - Stops the activity of the genes. Production of proteins stop.
How does this work?
Ex: E-coli bacteria only produces lactose-digesting enzymes in the presence of
lactose (double milk sugar). There is a lactose operon which causes this to
happen in the bacteria. (see diagram)
Why doesn’t the bacteria make the enzyme all the time?
Different genes are activated (turned on) in different cells.
Introns vs. Exons - introns do not code for proteins and are “cut out before
transcription.
Hox Genes – genes which control organs and tissues development in certain
of embryos. They determine body plan. Damage to a hox gene can
Go parts
to
Section:
lead to serious structure problems.
Chapter
12
Molecular Genetics
Hox Genes
 Hox genes are
responsible for
the general
body pattern of
most animals.
Section 12-5
Typical Gene Structure
Regulatory
sites
Promoter
(RNA polymerase
binding site)
Start transcription
Go to
Section:
DNA
strand
Stop transcription